"MDEV-8909 union parser cleanup" changes.

When the server parses a query like
  SELECT * FROM (SELECT 1);
a sequence of calls
  st_select_lex::init_nested_join() ..
  st_select_lex::end_nested_join()
was performed two times (tested in gdb).
Both pairs of calls seem to be redundant for a query
like this, because there are actually no any joins here.

This patch moved "table_ref_select" inside "select_derived",
which revealed that one the pairs was definitely redundant:
After this transformation we got an init_nested_join()
immediately followed by end_nested_join() for the same st_select_lex,
which has no any sense. So this pair of calls was removed.

to simplify further MDEV-8909 refactoring.

This was a bug in the parser. As a result it could accept queries
with invalid derived tables if they used With clauses.

- Moving "SELECT_SYM select_init2_derived opt_table_expression"
  from query_term into a new separate rule query_specification,
  and using query_specification in the beginning of query_term.
- query_term now does not have a %type, query_specification has a %type
  instead. This removes duplicate code that returns
  Lex->current_select->master_unit()->first_select();

between select_derived_union and query_expression_body.
An upcoming patch for MDEV-10035 will also reuse union_head_non_top.

- Moving select_options_and_item_list from select_init2
  to select_init and view_select_aux
- Renaming select_init2 to select_init3
This will simplify upcoming sql_yacc.yy fixes (e.g. MDEV-10035, MDEV-8909).

An addition to original patch:
- use FN_REFLEN instead of HOST_NAME_MAX (the latter can be undefined)
- avoid calling gethostname() on every prompt construction by caching it

Introduce `\H` option which behaves mostly like `\h`. The only exception is
when the client connects to the server hosted on localhost. In this case, the
hostname will be used instead.

closer the grammar in the SQL Standard:
- <query specification> is only a SELECT followed by
  <set quantifier>, <select list> and <table expression>.
- While <query term> includes SELECT queries and derived tables.

MDEV-10036 sql_yacc.yy: Split select_part2 to disallow syntactically bad constructs with INTO, PROCEDURE, UNION
MDEV-10037 UNION with LIMIT ROWS EXAMINED does not require parentheses

MDEV-10030 sql_yacc.yy: Split table_expression and remove PROCEDURE from create_select, select_paren_derived, select_derived2, query_specification

This change refactors the "table_expression" rule in sql_yacc.yy.

Queries with subselects and derived tables, as well as "CREATE TABLE ... SELECT"
now return syntax error instead of "Incorrect usage of PROCEDURE and ...".

This is an addition to original patch. Removed meaningless
"echo SET SESSION AUTOCOMMIT=0" (transaction is started explicitely on
master anyway).

- Don't log connection creation in galera_connect.inc

* simplify the code at default: label
* bugfix: flush the checksum for NULL fields
  (perfschema.checksum was failing)
* cleanup: put repeated code into a function

Error noted by Sergey Vojtovich.

Checksum implementations contain optimizations for calculating
checksums of larger blocks of memory.

This optimization calls my_checksum on a larger block of memory
rather than calling on multiple adjacent memory as its going though
the table columns for each table row.

- Change some static variables to dynamic to ensure that we don't do any memory
  allocations before server starts or stops
- Print more memory information on SIGHUP. Fixed output.
- Write out if memory was lost if run with --debug-at-exit
- Fixed wrong #ifdef in sql_cache.cc

- Avoid some realloc() during startup
- Ensure that file_key_management_plugin frees it's memory early, even if
  it's linked statically.
- Fixed compiler warnings from unused variables and missing destructors
- Fixed wrong indentation

MariaDB 10.1.x 32-bit binaries.

Problem was the fact that tablespace size was incorrectly
rounded to next extent size (1M).

wrong mutex usage from safe_mutex.
Ensure that LOCK_status is always taken before LOCK_thread_count

Problem was that cost_group_min_max() could not handle if group by was optimized away.