Making changes to wsrep_mysqld.h causes large parts of server code to
be recompiled. The reason is that wsrep_mysqld.h is included by
sql_class.h, even tough very little of wsrep_mysqld.h is needed in
sql_class.h. This commit introduces a new header file, wsrep_on.h,
which is meant to be included from sql_class.h, and contains only
macros and variable declarations used to determine whether wsrep is
enabled.
Also, header wsrep.h should only contain definitions that are also
used outside of sql/. Therefore, move WSREP_TO_ISOLATION* and
WSREP_SYNC_WAIT macros to wsrep_mysqld.h.

Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

ER_CHECK_NO_SUCH_TABLE was raised because a view does not have
the corresponding TABLE instance connected to TABLE_LIST and the
server interprets the absence as the absence of the table itself.

To fix the problem, we add a check to ensure that the target table
to be swapped with a partition is not a view.

Reviewed by: Nayuta Yanagisawa

When trying to execute ALTER TABLE EXCHANGE PARTITION with different
definitions, assertion

    table->s->db_create_options == part_table->s->db_create_options

failed in compare_table_with_partition().

However, this execution should not be allowed since executing
'exchange partition' requires the identical structure of the two tables.

To fix the problem, I deleted the assertion code and added code that
returns an error that indicates tables have different definitions.

Reviewed By: Nayuta Yanagisawa

The reason for this is to make all temporary file names similar and
also to be able to figure out from where a #sql-xxx name orginates.

New format is for most cases:
'#sql-name-current_pid-thread_id[-increment]'
Where name is one of subselect, alter, exchange, temptable or backup

The exceptions are:
ALTER PARTITION shadow files:
'#sql-shadow-thread_id-'original_table_name'

Names used with temp pool:
'#sql-name-current_pid-pool_number'