Using CREATE OR REPLACE TABLE is be identical to

DROP TABLE IF EXISTS table_name;
CREATE TABLE ...;

Except that:

* CREATE OR REPLACE is be atomic (now one can create the same table between drop and create).
* Temporary tables will not shadow the table name for the DROP as the CREATE TABLE tells us already if we are using a temporary table or not.
* If the table was locked with LOCK TABLES, the new table will be locked with the same lock after it's created.

Implementation details:
- We don't anymore open the to-be-created table during CREATE TABLE, which the original code did.
  - There is no need to open a table we are planning to create. It's enough to check if the table exists or not.
- Removed some of duplicated code for CREATE IF NOT EXISTS.
- Give an error when using CREATE OR REPLACE with IF NOT EXISTS (conflicting options).
- As a side effect of the code changes, we don't anymore have to internally re-prepare prepared statements with CREATE TABLE if the table exists.
- Made one code path for all testing if log table are in use.
- Better error message if one tries to create/drop/alter a log table in use
- Added back disabled rpl_row_create_table test as it now seams to work and includes a lot of interesting tests.
- Added HA_LEX_CREATE_REPLACE to mark if we are using CREATE OR REPLACE
- Aligned CREATE OR REPLACE parsing code in sql_yacc.yy for TABLE and VIEW
- Changed interface for drop_temporary_table() to make it more reusable
- Changed Locked_tables_list::init_locked_tables() to work on the table object instead of the table list object. Before this it used a mix of both, which was not good.
- Locked_tables_list::unlock_locked_tables(THD *thd) now requires a valid thd argument. Old usage of calling this with 0 i changed to instead call Locked_tables_list::reset()
- Added functions Locked_tables_list:restore_lock() and Locked_tables_list::add_back_last_deleted_lock() to be able to easily add back a locked table to the lock list.
- Added restart_trans_for_tables() to be able to restart a transaction.
- DROP_ACL is required if one uses CREATE TABLE OR REPLACE.
- Added drop of normal and temporary tables in create_table_imp() if CREATE OR REPLACE was used.
- Added reacquiring of table locks in mysql_create_table() and mysql_create_like_table()




mysql-test/include/commit.inc:
  With new code we get fewer status increments
mysql-test/r/commit_1innodb.result:
  With new code we get fewer status increments
mysql-test/r/create.result:
  Added testing of create or replace with timeout
mysql-test/r/create_or_replace.result:
  Basic testing of CREATE OR REPLACE TABLE
mysql-test/r/partition_exchange.result:
  New error message
mysql-test/r/ps_ddl.result:
  Fewer reprepares with new code
mysql-test/suite/archive/discover.result:
  Don't rediscover archive tables if the .frm file exists
  (Sergei will look at this if there is a better way...)
mysql-test/suite/archive/discover.test:
  Don't rediscover archive tables if the .frm file exists
  (Sergei will look at this if there is a better way...)
mysql-test/suite/funcs_1/r/innodb_views.result:
  New error message
mysql-test/suite/funcs_1/r/memory_views.result:
  New error message
mysql-test/suite/rpl/disabled.def:
  rpl_row_create_table should now be safe to use
mysql-test/suite/rpl/r/rpl_row_create_table.result:
  Updated results after adding back disabled test
mysql-test/suite/rpl/t/rpl_create_if_not_exists.test:
  Added comment
mysql-test/suite/rpl/t/rpl_row_create_table.test:
  Added CREATE OR REPLACE TABLE test
mysql-test/t/create.test:
  Added CREATE OR REPLACE TABLE test
mysql-test/t/create_or_replace-master.opt:
  Create logs
mysql-test/t/create_or_replace.test:
  Basic testing of CREATE OR REPLACE TABLE
mysql-test/t/partition_exchange.test:
  Error number changed as we are now using same code for all log table change issues
mysql-test/t/ps_ddl.test:
  Fewer reprepares with new code
sql/handler.h:
  Moved things around a bit in a structure to get better alignment.
  Added HA_LEX_CREATE_REPLACE to mark if we are using CREATE OR REPLACE
  Added 3 elements to end of HA_CREATE_INFO to be able to store state to add backs locks in case of LOCK TABLES.
sql/log.cc:
  Reimplemented check_if_log_table():
  - Simpler and faster usage
  - Can give error messages
  
  This gives us one code path for allmost all error messages if log tables are in use
sql/log.h:
  New interface for check_if_log_table()
sql/slave.cc:
  More logging
sql/sql_alter.cc:
  New interface for check_if_log_table()
sql/sql_base.cc:
  More documentation
  Changed interface for drop_temporary_table() to make it more reusable
  Changed Locked_tables_list::init_locked_tables() to work on the table object instead of the table list object. Before this it used a mix of both, which was not good.
  Locked_tables_list::unlock_locked_tables(THD *thd) now requires a valid thd argument.  Old usage of calling this with 0 i changed to instead call Locked_tables_list::reset()
  Added functions Locked_tables_list:restore_lock() and Locked_tables_list::add_back_last_deleted_lock() to be able to easily add back a locked table to the lock list.
  Check for command number instead of open_strategy of CREATE TABLE was used.
  Added restart_trans_for_tables() to be able to restart a transaction.  This was needed in "create or replace ... select" between the drop table and the select.
sql/sql_base.h:
  Added and updated function prototypes
sql/sql_class.h:
  Added new prototypes to Locked_tables_list class
  Added extra argument to select_create to avoid double call to eof() or send_error()
  - I needed this in some edge case where the table was not created against expections.
sql/sql_db.cc:
  New interface for check_if_log_table()
sql/sql_insert.cc:
  Remember position to lock information so that we can reaquire table lock for LOCK TABLES + CREATE OR REPLACE TABLE SELECT. Later add back the lock by calling restore_lock().
  Removed one not needed indentation level in create_table_from_items()
  Ensure we don't call send_eof() or abort_result_set() twice.
sql/sql_lex.h:
  Removed variable that I temporarly added in an earlier changeset
sql/sql_parse.cc:
  Removed old test code (marked with QQ)
  Ensure that we have open_strategy set as TABLE_LIST::OPEN_STUB in CREATE TABLE
  Removed some IF NOT EXISTS code as this is now handled in create_table_table_impl().
  Set OPTION_KEEP_LOGS later. This code had to be moved as the test for IF EXISTS has changed place.
  DROP_ACL is required if one uses CREATE TABLE OR REPLACE.
sql/sql_partition_admin.cc:
  New interface for check_if_log_table()
sql/sql_rename.cc:
  New interface for check_if_log_table()
sql/sql_table.cc:
  New interface for check_if_log_table()
  Moved some code in mysql_rm_table() under a common test.
  - Safe as temporary tables doesn't have statistics.
  - !is_temporary_table(table) test was moved out from drop_temporary_table() and merged with upper level code.
  - Added drop of normal and temporary tables in create_table_imp() if CREATE OR REPLACE was used.
  - Added reacquiring of table locks in mysql_create_table() and mysql_create_like_table()
  - In mysql_create_like_table(), restore table->open_strategy() if it was changed.
  - Re-test if table was a view after opening it.
sql/sql_table.h:
  New prototype for mysql_create_table_no_lock()
sql/sql_yacc.yy:
  Added syntax for CREATE OR REPLACE TABLE
  Reuse new code for CREATE OR REPLACE VIEW
sql/table.h:
  Added name for enum type
sql/table_cache.cc:
  More DBUG