Made sure that join buffers could be used for inner tables of
any semi-join when the first match strategy is employed.

it's working on the WHERE clause.

Re-worked fix of Tor Didriksen:
 The problem was that fix_after_pullout() after semijoin conversion 
 wasn't propagated from the view to the underlying table. 
 On subesequent executions of the prepared statement, 
 we would mark the underlying table as 'dependent' and the predicate 
 anlysis would lead to a different (and illegal) execution plan.

for table elimination in debug builds.
(part 2)

for table elimination in debug builds.

In Item_ref::fix_fields() do invoke mark_as_dependent() for outside 
references in all cases (see email for more details)

sql/item.cc:
  In Item_ref::fix_fields() do invoke mark_as_dependent() for outside references in all cases.
sql/item.h:
  Change Field_enumerator to enumerate Item_field-s not Field-s.
sql/item_subselect.cc:
  Change Field_enumerator to enumerate Item_field-s not Field-s.
sql/opt_table_elimination.cc:
  Change Field_enumerator to enumerate Item_field-s not Field-s.

  Don't go into branch that calls upper_refs.empty() more than once per
  PREPARE or EXECUTE
* Avoid crashing when processing references to outside from subquery's HAVING
  (will explain in more details in email)

sql/item.h:
  * Avoid crashing when processing references to outside from subquery's HAVING
    (will explain in more details in email)
sql/item_subselect.cc:
  * Better self-recursion protection in Item_subselect::fix_fields. 
    Don't go into branch that calls upper_refs.empty() more than once per
    PREPARE or EXECUTE

prepared statements: re-collect list of upper refs on every PS re-execution.

- More test results updates (checked)

- Update test results
- More comments
- Add Item_in_optimizer::transform() which was lost in backport

- Factor out subquery code into sql/opt_subselect.{h,cc}
- Stop using the term "confluent" (was used due to misreading the dictionary)

- Variant #3 of the fix. It also
 = Unifies code with table elimination's 
 = is able to handle FROM-subquery pullout.

- Fix valgrind failure: do initialize Item::is_expensive_cache.

XOR conditions are not optimized, and Item_cond_xor therefore
acts like type Func_item even though it inherits from Item_cond.
A subtle difference between Item_func and Item_cond is that
you can get the children Items from the former by calling
arguments(), and from the latter by calling argument_list().
However, since Item_cond_xor inherits from Item_cond,
arguments() did not return any Items.

The fact that Item_cond_xor::arguments() did not return it's
children items lead to a problem for make_cond_for_index();
the method accepted that XOR items on unindexed columns were
pushed using ICP. ICP evaluation of non-indexed columns
does not (and should not) work.

The fix for this bug is to make Item_cond_xor return it's
children items when the arguments() method is used. This makes
Item_cond_xor behave more like Item_func and in turn allows
make_cond_for_index() to discover any conflicting children
Items.

This is a temporary fix and should be removed when Item_cond_xor
 is optimized.

process temporary table overflow correctly.

- Backport into Maria DB 5.3, part 1

- Enable semi-join handling in the join cache code

- Fix valgrind failure
- Test result fixes (not finished)

There are still test failures because of:
- Wrong query results in outer join + semi join
- EXPLAIN output differences

- Do call update_used_tables() for new conditions obtained when adding
  outer join's triggered conditions. Correct values of used_tables() are
  now needed for condition pushdown.
- Update test results

mysql-test/suite/pbxt/r/join_outer.result:
  DS-MRR backport:
  - Update test results
sql/sql_select.cc:
  DS-MRR backport: fix buildbot valgrind failures:
  - Do call update_used_tables() for new conditions obtained when adding
    outer join's triggered conditions. Correct values of used_tables() are
    now needed for condition pushdown.

- Add opt_range_mrr.cc file into source repo

mysql-test/r/myisam_mrr.result:
  Make testcase work for both debug and release
mysql-test/t/myisam_mrr.test:
  Make testcase work for both debug and release
sql/Makefile.am:
  - Add opt_range_mrr.cc file into source repo

- Make index condition pushdown be controlled by an @@optimizer_switch flag,
  not by @@engine_condition_pushdown
- Make MRR buffer size be controlled by @@mrr_buffer_size, not 
  by @@read_rnd_buffer_size
- Move parts of code to separate files
- Code cleanup
- Add --sorted_result to some SELECTs in tests.

WL#2771 "Block Nested Loop Join and Batched Key Access Join"

- Fix PBXT test results (PBXT doesn't support MRR or ICP, but we get result 
  diffs because we've also backported a fix that
  - prints out "Using where" when the table has part of WHERE that it has 
    got from LEFT JOIN's ON expression
  - Does a better job at removing equalities that are guaranteed to be true 
    by use of ref acccess.