Any Field object should use current_thd instead of table->in_use 
when THD is needed if table == NULL.
This patch fixes the crash of test case from mdev-504.test.

Opening system statistical tables and reading statistical data from 
them for a regular table should be done after opening and locking 
this regular table.
No test case is provided with this patch.

If a table is already in the table cache but without data from persistent
statistical tables then the function open_and_process_table should not
only allocate memory for this statistical data in the corresponding
TABLE_SHARE object, but also should copy the references to the data into
certain fields of the TABLE data structure: for each key of the table 
KEY::read_stats should be copied, and for each column of the table
Field::read_stats should be copied. 

Split ER_NO_SUCH_TABLE into ER_NO_SUCH_TABLE and ER_NO_SUCH_TABLE_IN_ENGINE to be able to distingus if a .frm file is missing or if the table is missing in the engine.


sql/handler.cc:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/rpl_record.cc:
  Fixed wrong printf
sql/share/errmsg-utf8.txt:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/sp.cc:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/sp_head.cc:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/sql_admin.cc:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/sql_base.cc:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/sql_show.cc:
  Added ER_NO_SUCH_TABLE_IN_ENGINE
sql/table.cc:
  Fixed typo

MDEV-405: Server crashes in test_if_skip_sort_order on EXPLAIN with GROUP BY and HAVING in EXISTS subquery
- Testcase

- Don't do early cleanup of uncorrelated subqueries if we're running an EXPLAIN.

        the fill_help_table-5.5.sql file was copied into mariadb.

per-file comments:
  scripts/fill_help_tables.sql
        MDEV-471 update help tables.

The function collect_statistics_for_table() when scanning a table
did not take into account that the handler function ha_rnd_next
could return the code HA_ERR_RECORD_DELETE that should not be
considered as an indication of an error.
Also fixed a potential memory leak in this function.

force -fno-strict-aliasing for oqgraph

The problem was that was_null and null_value variables was reset in each reexecution of IN subquery, but engine rerun only for non-constant subqueries.

Fixed checking constant in Item_equal sort.
Fix constant reporting in Item_subselect.

Various places in the server replication code was incorrectly quoting
strings, which could lead to incorrect SQL on the slave/mysqlbinlog.

With the new code of mysql-5.5 for metadata locking the function
unlock_tables_n_open_system_tables_for_write should not explicitly
unlock tables for which external locks have been set and should not
explicitly reset thd->lock to 0.
 

fix mysys/waiting_threads.c to compile w/o performance schema
include clients. scripts and manpages in -DWITHOUT_SERVER

only add cmake as a build dependency for distributions, where cmake is recent enough

Item::get_date() should return 1 unless the value is a valid date.