When the GROUP BY clause contains a column reference that can be resolved to
both an aliased column in the SELECT list, and to a column in the FROM clause,
the group column is resolved to the column in the FROM clause (for ANSI conformance).
However, it may be so that the user's intent is just the other way around, and he/she
gets the query results grouped by a completely different column than expexted.
This patch adds a warning in such cases that tells the user that there is potential
ambiguity in the group column.

sql/sql_select.cc
- Added a warning when a GROUP column is ambiguous due to that there is a
  column reference with the same name both in the SELECT and FROM clauses.
  In this case we resolve to the column in FROM clause and warn the user
  of a possible ambiguity.
- More extensive comments.
- Changed the function to return bool instead of int (as in other places).

mysql-test/t/group_by.test
  Added test for BUG#11211.

mysql-test/r/group_by.result
  Added test for BUG#11211.

into mysql.com:/home/cps/mysql/trees/mysql-5.0

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

into  moonbone.local:/work/mysql-5.0-bug-11111

Wrong method for creating temporary field was choosen, which results in
sending int field with int header but lonlong data.

Test case is added to mysql_client_test.c because client library is required
to test the bug.

into deer.(none):/home/hf/work/mysql-5.0.clean

into mysql.com:/home/timka/mysql/src/5.0-bug-11044

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

into mysql.com:/home/timka/mysql/src/5.0-bug-11044

The problem was that when there was no MIN or MAX function, after finding the
group prefix based on the DISTINCT or GROUP BY attributes we did not search further
for a key in the group that satisfies the equi-join conditions on attributes that
follow the group attributes. Thus we ended up with the wrong rows, and subsequent
calls to select_cond->val_int() in evaluate_join_record() were filtering those
rows. Hence - the query result set was empty.

The problem occured both for GROUP BY queries without MIN/MAX and for queries
with DISTINCT (which were internally executed as GROUP BY queries).

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

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

into dl145c.mysql.com:/home/ndbdev/tomas/mysql-4.1

into dl145c.mysql.com:/home/ndbdev/tomas/mysql-4.1

  Correction for test case of bug #11142.

  Added a test case for bug #11142.
item_cmpfunc.cc:
  Fixed bug #11142.
  Implementation of Item_func_nullif::is_null was corrected.

  Logging to logging@openlogging.org accepted
DbtcMain.cpp, testTimeout.cpp:
  Bug  #11290 TransactionInactiveTimeout = 0 does not result in infinite timeout

into igor-inspiron.creware.com:/home/igor/mysql-5.0

into igor-inspiron.creware.com:/home/igor/dev/mysql-4.1-0

  Add a patch by Georg Richter to remove compiler warnings on 64-bit Windows

into mysql.com:/home/svoj/devel/yassl-mysql-5.0

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

  Added a test case for bug #11167.
sql_select.cc:
  Fixed bug #11167.
  In 4.1 char/varchar fields are limited by 255 characters in
  length that make them longer than 255 bytes in size for such
  character sets as UTF8. The functions store_record_in_cache
  and read_cached_records did not take into account this
  Moreover the code did not take into account that the size
  of the varchar fields in 5.0 can be up to 65535 bytes

into mysql.com:/home/svoj/devel/yassl-mysql-5.0

into mysql.com:/home/svoj/devel/yassl-mysql-5.0

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

into mysql.com:/home/bk/b6883-mysql-4.1