- Rearrange spawn worker code

Backporting fixes to 5.1 from 6.0.

When executing a DROP DATABASE statement in ROW mode and having temporary
tables open at the same time, the existance of temporary tables prevent
the server from switching back to row mode after temporarily switching to
statement mode to handle the logging of the statement.

Fixed the problem by removing the code to switch to statement mode and added
code to temporarily disable the binary log while dropping the objects in the
database.

The failure was caused by executing a CREATE-SELECT statement that creates a
table in another database than the current one. In row-based logging, the
CREATE statement was written to the binary log without the database, hence
creating the table in the wrong database, causing the following inserts to
fail since the table didn't exist in the given database.

Fixed the bug by adding a parameter to store_create_info() that will make
the function print the database name before the table name and used that
in the calls that write the CREATE statement to the binary log. The database
name is only printed if it is different than the currently selected database.

The output of SHOW CREATE TABLE has not changed and is still printed without
the database name.

The problem was because the event allocated in mysql_client_binlog_statement
was not freed when an error occured while applying the event.

pb notices differences in results at the very beginning of the test.

Absense of mysql.ndb_apply_status must be benign anyway, but the warning should not happen
if have_ndb.inc is invoked ahead of ndb_master-slave.
Fixed with relocation of the macros.

BUG#38369, enable rpl_row_basic_7ndb test

Post-merge fix: mysql_client_test.c is compiled by C compilers
and some C compilers don't support mixed declarations and code
and it's explicitly forbidden by ISO C90.

Note: NULL merge of sql/sql_yacc.yy, the fix for bug#38296 will be provided separately for 5.1

Fixed missing DBUG_RETURN in the function find_key_block

This fix is for 5.0 only : back porting the 6.0 patch manually

The parser code in sql/sql_yacc.yy needs to be more robust to out of
memory conditions, so that when parsing a query fails due to OOM,
the thread gracefully returns an error.

Before this fix, a new/alloc returning NULL could:
- cause a crash, if dereferencing the NULL pointer,
- produce a corrupted parsed tree, containing NULL nodes,
- alter the semantic of a query, by silently dropping token values or nodes

With this fix:
- C++ constructors are *not* executed with a NULL "this" pointer
when operator new fails.
This is achieved by declaring "operator new" with a "throw ()" clause,
so that a failed new gracefully returns NULL on OOM conditions.

- calls to new/alloc are tested for a NULL result,

- The thread diagnostic area is set to an error status when OOM occurs.
This ensures that a request failing in the server properly returns an
ER_OUT_OF_RESOURCES error to the client.

- OOM conditions cause the parser to stop immediately (MYSQL_YYABORT).
This prevents causing further crashes when using a partially built parsed
tree in further rules in the parser.

No test scripts are provided, since automating OOM failures is not
instrumented in the server.
Tested under the debugger, to verify that an error in alloc_root cause the
thread to returns gracefully all the way to the client application, with
an ER_OUT_OF_RESOURCES error.