resulted in a wrong error message.

The nest_level counter indicates the depth of nesting for a subselect. It is
needed to properly resolve aggregate functions in nested subselects. Obviously 
it shouldn't be incremented for UNION parts because they have the same level of
nesting. This counter was incremented by 1 in the mysql_new_select() function
for any new select and wasn't decremented for UNION parts. This resulted in
wrongly reported error messages.

Now the nest_level counter is decremented by 1 for any union part.

  After merge fix

into moonbone.local:/work/18360-bug-4.1-mysql-opt

The IN() function uses agg_cmp_type() to aggregate all types of its arguments
to find out some common type for comparisons. In this particular case the 
char() and the int was aggregated to double because char() can contain values
like '1.5'. But all strings which do not start from a digit are converted to
0. thus 'a' and 'z' become equal. 
This behaviour is reasonable when all function arguments are constants. But 
when there is a field or an expression this can lead to false comparisons. In
this case it makes more sense to coerce constants to the type of the field
argument.

The agg_cmp_type() function now aggregates types of constant and non-constant
items separately. If some non-constant items will be found then their
aggregated type will be returned. Thus after the aggregation constants will be
coerced to the aggregated type. 

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

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

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

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

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

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

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

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

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

In multi-table delete a table for delete can't be used for selecting in
subselects. Appropriate error was raised but wasn't checked which leads to a
crash at the execution phase.

The mysql_execute_command() now checks for errors before executing select
for multi-delete.

into  mysql.com:/home/emurphy/iggy/mysql-5.0

into  mysql.com:/home/kgeorge/mysql/5.0/clean

into  mysql.com:/home/kgeorge/mysql/5.0/B18681

into  mysql.com:/home/kgeorge/mysql/5.0/B18681

into  mysql.com:/home/kgeorge/mysql/5.0/B14875

When reading a view definition from a .frm file it was
throwing a SQL error if the DEFINER user is not defined.
Changed it to a warning to match the (documented) case
when a view with undefined DEFINER user is created.

The check for view security was lacking several points :
1. Check with the right set of permissions : for each table ref that
participates in a view there were the right credentials to use in it's
security_ctx member, but these weren't used for checking the credentials.
This makes hard enforcing the SQL SECURITY DEFINER|INVOKER property
consistently.
2. Because of the above the security checking for views was just ruled out
in explicit ways in several places.
3. The security was checked only for the columns of the tables that are
brought into the query from a view. So if there is no column reference
outside of the view definition it was not detecting the lack of access to
the tables in the view in SQL SECURITY INVOKER mode.

The fix below tries to fix the above 3 points.

into  mysql.com:/space/pekka/ndb/version/my50-bug14509

into  mysql.com:/space/pekka/ndb/version/my50-bug14509

into  mysql.com:/home/kgeorge/mysql/5.0/clean

into  mysql.com:/home/kgeorge/mysql/5.0/B18742-2

into  mysql.com:/home/kgeorge/mysql/5.0/B18742-2

into  mysql.com:/home/kgeorge/mysql/5.0/B19700

  
The unsigned flag in Item was not propagated through the single value subqueries.
This caused the result to be treated as signed.

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

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

Replaced COND_refresh with COND_global_read_lock becasue of a bug in NTPL threads when using different mutexes as arguments to pthread_cond_wait()
The original code caused a hang in FLUSH TABLES WITH READ LOCK in some circumstances because pthread_cond_broadcast() was not delivered to other threads.
This fixes:
Bug#16986: Deadlock condition with MyISAM tables
Bug#20048: FLUSH TABLES WITH READ LOCK causes a deadlock

into  april.(none):/home/svoj/devel/mysql/BUG17001/mysql-5.0