Added options for each compression type that can be disabled i.e.
bzip2, lz4, lzma and lzo.

* reset current_thd in THD::~THD, otherwise my_malloc_size_cb_func()
  might access THD after it was destroyed.
* remove now redundant set_current_thd(0) calls that follow delete thd.

This reverts commit 06c16904.

* error reporting was never needed
* avoid useless transformaton hton to db_type to hton
* in many cases the engine was guaranteed to exist, add asserts
* use ha_default_handlerton() instead of ha_checktype(DB_TYPE_DEFAULT)

but keep the code cleanup.
as it turns out, it didn't change the behavior, which is good :)

Now this works the same way as all other multi source variables.

Extend interface for 'show variables' with current scope

in case args[0] changes between PREPARE and EXECUTE

in particular, not the one that destructively changes Item's charset
(meaning different metadata for PREPARE and EXECUTE)

* fix the test to pass
* rearrange tests in a file to allow it to auto-merge in the future

use the old registry branch, even if we changed the "manufacturer" string

MDEV-7024: Assertion `! is_set()' failed in Diagnostics_area::set_eof_status on executing ANALYZE SELECT via PS

select_send::is_result_interceptor() should return FALSE because it return results to the client.

added a script to regenerate certificates easily in the future (2035!)
restored server8k-key.pem to actually be 8K key, as it was supposed to

MDEV-7023: Error 2027: Malformed packet and assertion `field_types == 0 || field_types[field_pos] == MYSQL_TYPE_INT24 || field_types[field_pos] == MYSQL_TYPE_LONG' failure in Protocol_text::store_long

The problem was that sp_head::MULTI_RESULTS was not set correctly for ANALYZE statement.

Backport from mysql 5.7. The patch reviewed, test added.

bzr merge -r4588 maria/10.0

Merged revision 5224 from mysql-5.6 and added a test case.
..
revno: 5224
committer: Sergey Glukhov <sergey.glukhov@oracle.com>
branch nick: mysql-5.6
timestamp: Wed 2013-06-19 14:24:08 +0400
message:
    Bug#16620047 INCORRECT QUERY RESULT (AFTER SERVER UPGRADE)

Backport from 10.1.

MDEV-6668: Server crashes in check_view_single_update on concurrent DDL/DML flow with views and triggers

Call mysql_derived_reinit() if we are reusing view.
This is needed as during a previous error condition the view may not have been reset

sql/sql_derived.cc:
  More DBUG_PRINT
  Always reset merged_for_insert (no reason to not do that)
sql/sql_derived.h:
  Added prototype
sql/sql_insert.cc:
  More DBUG_PRINT
  Added DBUG_ASSERT
sql/sql_view.cc:
  Call mysql_derived_reinit() if we are reusing view.
  This is needed as during a previous error condition the view may not have been reset
sql/table.cc:
  More DBUG_PRINT