MDEV-4326 fix.

Removed "optimization" which caused preoblems on second execution of PS with string parameter in LIMIT clause.

Fixed test_bug43560 to be able to skipp it if connection is UNIX socket.
Made consistent handling of the predicates of the form
<non-nullable datatime field> IS NULL in outer joins with
that in inner joins.
Previously such condition was transformed into the condition
<non-nullable datatime field> = 0 unless the field belonged
to an inner table of an outer join. In this case the predicate
was interpreted as for any other field.
Now if the field in the predicate <non-nullable datatime field> IS NULL
belongs to an inner table of an outer join the predicate is 
transformed into the disjunction
<non-nullable datatime field> = 0 OR <non-nullable datatime field> IS NULL.
This is fully compatible with the semantics of such predicates in 5.5.
Fixed bug mdev-4336.
When iterating over a list of conditions using List_iterator
the function remove_eq_conds should skip all predicates that
replace a condition from the list. Otherwise it can come to
an infinite recursion.
MDEV-4482: main.windows test fails in buildbot with result mismatch
- Rollback an earlier patch (was pushed into 5.3 instead of 5.5)
Merge
MDEV-4290:
Fix agregate function resolution in derived tables (no name resolution over a derived table border)
MDEV-4462 mysqld gets SIGFPE when mysql.user table is empty

avoid divison by zero
MDEV-4280: Assertion `empty_size == empty_size_on_page' failure in ma_blockrec.c or ER_NOT_KEYFILE on query with DISTINCT and GROUP BY
This could happen when using Aria for internal temporary files (default case) and using DISTINCT.
_ma_scan_restore_block_record() didn't work correctly if there was rows inserted, updated or deleted on the handler
between calls to _ma_scan_remember_block_record() and _ma_scan_restore_block_record().
The effect was that some DISTINCT queries that used remove_dup_with_compare() could fail.
Fixed compiler warning
Fixed compiler failure on solaris
Fix cpack error - safe_process.pl does not exist anymore.
MDEV-4544 - update MSI to include HeidiSQL 8.0
5.1 merge
5.2 merge
fixes for buildbot
MDEV-4575 MySQL client doesn't strip off 5.5.5- prefix while connecting to 10.x server

extend 5.1 client library to read 4 byte capabilities from the first handshake packet.
two higher bytes are always zeros for 5.1 servers.
MDEV-4593: p_s: crash in simplify_joins with delete using subselect from view

mysql_derived_merge_for_insert() should not be called for views or derived tables which are not put (directly or via other views) in main SELECT_LEX "join list".
MDEV-4651 Crash in my_decimal2decimal in a ORDER BY query

modified:
  mysql-test/r/ps_2myisam.result
  mysql-test/r/ps_3innodb.result
  mysql-test/r/ps_4heap.result
  mysql-test/r/ps_5merge.result
  mysql-test/r/type_datetime_hires.result
  mysql-test/suite/maria/r/ps_maria.result
  mysql-test/t/type_datetime_hires.test
  sql/item_timefunc.h
MDEV-4635 Crash in UNIX_TIMESTAMP(STR_TO_DATE('2020','%Y'))

modified:
  mysql-test/r/func_time.result
  mysql-test/t/func_time.test
  sql/item_timefunc.cc
  sql/mysql_priv.h
MDEV-4634 Crash in CONVERT_TZ
Item_func_min_max::get_date() did not check the
returned value against the fuzzy_date flags, so
it could return a bad value to the caller that
expects a good date (e.h. CONVERT_TZ).


modified:
  mysql-test/r/type_date.result
  mysql-test/r/type_datetime.result
  mysql-test/r/type_time.result
  mysql-test/t/type_date.test
  mysql-test/t/type_datetime.test
  mysql-test/t/type_time.test
  sql/item_func.cc
  sql/item_timefunc.cc
  sql/mysql_priv.h
  sql/time.cc