Bug#19022 "Memory bug when switching db during trigger execution"
 Bug#17199 "Problem when view calls function from another database."
 Bug#18444 "Fully qualified stored function names don't work correctly in
            SELECT statements"

 Documentation note: this patch introduces a change in behaviour of prepared
 statements.

 This patch adds a few new invariants with regard to how THD::db should
 be used. These invariants should be preserved in future:

  - one should never refer to THD::db by pointer and always make a deep copy
    (strmake, strdup)
  - one should never compare two databases by pointer, but use strncmp or
    my_strncasecmp
  - TABLE_LIST object table->db should be always initialized in the parser or
    by creator of the object.

    For prepared statements it means that if the current database is changed
    after a statement is prepared, the database that was current at prepare
    remains active. This also means that you can not prepare a statement that
    implicitly refers to the current database if the latter is not set.
    This is not documented, and therefore needs documentation. This is NOT a
    change in behavior for almost all SQL statements except:
     - ALTER TABLE t1 RENAME t2 
     - OPTIMIZE TABLE t1
     - ANALYZE TABLE t1
     - TRUNCATE TABLE t1 --
     until this patch t1 or t2 could be evaluated at the first execution of
     prepared statement. 

     CURRENT_DATABASE() still works OK and is evaluated at every execution
     of prepared statement.

     Note, that in stored routines this is not an issue as the default
     database is the database of the stored procedure and "use" statement
     is prohibited in stored routines.

  This patch makes obsolete the use of check_db_used (it was never used in the
  old code too) and all other places that check for table->db and assign it
  from THD::db if it's NULL, except the parser.

 How this patch was created: THD::{db,db_length} were replaced with a
 LEX_STRING, THD::db. All the places that refer to THD::{db,db_length} were
 manually checked and:
  - if the place uses thd->db by pointer, it was fixed to make a deep copy
  - if a place compared two db pointers, it was fixed to compare them by value
    (via strcmp/my_strcasecmp, whatever was approproate)
 Then this intermediate patch was used to write a smaller patch that does the
 same thing but without a rename.

 TODO in 5.1:
   - remove check_db_used
   - deploy THD::set_db in mysql_change_db

 See also comments to individual files.

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into  zippy.(none):/home/cmiller/work/mysql/mysql-5.0

into  shellback.(none):/home/msvensson/mysql/mysql-5.0

into  perch.ndb.mysql.com:/home/jonas/src/mysql-5.0

into  shellback.(none):/home/msvensson/mysql/mysql-5.0-maint

into  perch.ndb.mysql.com:/home/jonas/src/mysql-5.0

into  perch.ndb.mysql.com:/home/jonas/src/mysql-5.0

into  mysql.com:/home/marty/MySQL/mysql-5.0

into  perch.ndb.mysql.com:/home/jonas/src/50-work

  Dont be too aggressive in Dbtc::nodeFailCheckTransaction
  let it timeout by 1, so that it does not assert that it has waited too long
  old impl. set timeotu value to 0, making timeout = (ctcTimer - 0) which could be quite big.

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into  devsrv-b.mysql.com:/users/msvensson/mysql-5.0

 - avoid allocating memory for each call to 'EVP_md5' and 
   'EVP_des_ede3_cbc' which were not released until server was stopped
 - Those functions are used from the SQL function 'des_encrypt' and
   'des_decrypt'.

adapting to pushbuild's custom to switch from default pathes. The name for
var directory must be set with MYSQLTEST_VARDIR.

into  shellback.(none):/home/msvensson/mysql/mysql-5.0

 - Part 1, fixes rpl- and federated-tests where connection is made to 127.0.0.1

 - Include prefix files that renames all public functions in yaSSLs
   OpenSSL API to ya<function_name>. They will otherwise conflict
   with OpenSSL functions if loaded by an application that uses OpenSSL
   as well as libmysqlclient with yaSSL support.

into  mysql.com:/home/marty/MySQL/mysql-5.0

Two threads both try a shutdown sequence which creates a race to the
de-init/free of certain resources.

This exists in similar form in the client as 17926: "mysql.exe crashes
when ctrl-c is pressed in windows."

missed table to drop after merge from 4.1 

into  dl145k.mysql.com:/tmp/andrei/MERGE/5.0

into  shellback.(none):/home/msvensson/mysql/mysql-5.0

into  mysql.com:/space/pekka/ndb/version/my50

into  mysql.com:/mnt/storeage/mysql-5.0-maint_bug18669

into  mysql.com:/usr/home/ram/work/mysql-5.0

into  mysql.com:/home/alik/MySQL/devel/5.0-tree

into  mysql.com:/usr/home/ram/work/mysql-5.0

into  rurik.mysql.com:/home/igor/mysql-4.1

refers to a column name.

Bug#18282 "INFORMATION_SCHEMA.TABLES provides inconsistent info about invalid views"
This bug caused crashes or resulted in wrong data being returned
when one tried to obtain information from I_S tables about views
using stored functions.

It was caused by the fact that we were using LEX representing
statement which were doing select from I_S tables as active LEX
when contents of I_S table were built. So state of this LEX both
affected and was affected by open_tables() calls which happened
during this process. This resulted in wrong behavior and in
violations of some of invariants which caused crashes.

This fix tries to solve this problem by properly saving/resetting
and restoring part of LEX which affects and is affected by the
process of opening tables and views in get_all_tables() routine.
To simplify things we separated this part of LEX in a new class
and made LEX its descendant.

into  mysql.com:/space/pekka/ndb/version/my50