Add more comments to row_search_for_mysql() and remove the ugly double use of the variable rec in that function

into  hundin.mysql.fi:/home/heikki/mysql-5.0

into  mysql.com:/home/kostja/mysql/mysql-5.0-dsql3

The idea of the patch is to separate statement processing logic,
such as parsing, validation of the parsed tree, execution and cleanup, 
from global query processing logic, such as logging, resetting
priorities of a thread, resetting stored procedure cache, resetting
thread count of errors and warnings.
This makes PREPARE and EXECUTE behave similarly to the rest of SQL
statements and allows their use in stored procedures.
This patch contains a change in behaviour:
until recently for each SQL prepared statement command, 2 queries
were written to the general log, e.g.
[Query]   prepare stmt from @stmt_text;
[Prepare] select * from t1 <-- contents of @stmt_text
The chagne was necessary to prevent [Prepare] commands from being written
to the general log when executing a stored procedure with Dynamic SQL.
We should consider whether the old behavior is preferrable and probably
restore it.
This patch refixes Bug#7115, Bug#10975 (partially), Bug#10605 (various bugs
in Dynamic SQL reported before it was disabled).

  Fix bug #12947 : a consistent read could return inconsistent results; this bug was introduced in 5.0.5

into  mysql.com:/home/jimw/my/mysql-5.0-clean

into  mysql.com:/home/jimw/my/mysql-4.1-clean

into  sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

- current_arena to stmt_arena: the thread may have more than one
'current' arenas: one for runtime data, and one for the parsed 
tree of a statement. Only one of them is active at any moment.
- set_item_arena -> set_query_arena, because Item_arena was renamed to 
Query_arena a while ago
- set_n_backup_item_arena -> set_n_backup_active_arena;
the active arena is the arena thd->mem_root and thd->free_list
are currently pointing at.
- restore_backup_item_arena -> restore_active_arena (with the same
rationale)
- change_arena_if_needed -> activate_stmt_arena_if_needed; this
method sets thd->stmt_arena active if it's not done yet.

into  sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

into  eel.(none):/home/jonas/src/mysql-5.0-push

into  eel.(none):/home/jonas/src/mysql-5.0-push

into  eel.(none):/home/jonas/src/mysql-5.0-push

into  eel.(none):/home/jonas/src/mysql-5.0

into  mysql.com:/users/lthalmann/bk/mysql-5.0

  Always abort if node failure occured between startTransaction and commit
  (can later be improved by wl#2610)

  make sure not to cut log to early 
  (specificly not use LCP with maxGciStarted that has not yet completed)

into  neptunus.(none):/home/msvensson/mysql/mysql-4.1

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

into  mysql.com:/users/lthalmann/bk/mysql-5.0

into  mysql.com:/usr/home/bar/mysql-4.1.b12363

into  sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

into  sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

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

into  mysql.com:/usr/home/bar/mysql-4.1.b12363

into  mysql.com:/usr/home/bar/mysql-5.0

  Fix crash reported in bug 12849.
  It doesn't fix the whole problem though.
  Let Pem fix it later.

into  mysql.com:/users/lthalmann/bk/mysql-4.1-bug12542

into  mysql.com:/home/dlenev/src/mysql-5.0-merges

and GRANT in multi-threaded environment" into 5.0 tree.

into  sanja.is.com.ua:/home/bell/mysql/bk/work-bug3-5.0

into  mysql.com:/home/dlenev/src/mysql-5.0-merges