filesystem case sensitivity.

Hostname can include characters, which are invalid for use as filename,
thus case sensitivity test will fail to produce meaningful results.

Test crashes server intentionally, need to be prepared for
crash recovery and database page corruption.

Postfix: The pre-initialization of wsrep threads is not needed
for mysqldump sst method.

when they're not needed anymore. Helps when
daemonizing it from mysql.init

Fixed the remaining failing test case in 10.1

MDEV-10716: Assertion `real_type() != FIELD_ITEM' failed in Item_ref::build_equal_items(THD*, COND_EQUAL*, bool, COND_EQUAL**)

Degenerated condition in AND should be treated in the same
way as in WHERE/HAVING alone (i.e reference should be
processed as well as fields)

When a BF thread attempts to abort a victim thread's transaction,
the victim thread is not locked and thus its not safe to rely on
its data structures like htons registered for the trx.

So, instead of getting the registered htons from victim, innodb's
hton can be looked up directly from installed_htons[] and used to
abort the transaction. (Same technique is used in older versions)

Perform a post initialization of plugin-related variables
of wsrep threads after their global counterparts have been
initialized.

The crash is caused due to a race condition where wsrep
startup threads invoke ha_maria::implicit_commit() method
while maria_hton is partially initialized. The fix is to
skip this method if plugins are uninitialized.

update info->write_end and info->write_pos together, with no
"return on error" in between, otherwise write_end might end up being
smaller than write_pos

initialize uninitialized value

- storage/innobase/dict/dict0stats.cc
- storage/xtradb/dict/dict0stats.cc

(Fixing both InnoDB and XtraDB)

Re-opening a TABLE object (after e.g. FLUSH TABLES or open table cache
eviction) causes ha_innobase to call
dict_stats_update(DICT_STATS_FETCH_ONLY_IF_NOT_IN_MEMORY).

Inside this call, the following is done:
  dict_stats_empty_table(table);
  dict_stats_copy(table, t);

On the other hand, commands like UPDATE make this call to get the "rows in
table" statistics in table->stats.records:

  ha_innobase->info(HA_STATUS_VARIABLE|HA_STATUS_NO_LOCK)

note the HA_STATUS_NO_LOCK parameter. It means, no locks are taken by
::info() If the ::info() call happens between dict_stats_empty_table
and dict_stats_copy calls, the UPDATE's optimizer will get an estimate
of table->stats.records=1, which causes it to pick a full table scan,
which in turn will take a lot of row locks and cause other bad
consequences.

Also add fallback version string for unknown future versions.

On OS X with clang 7.3.0 running any test as embedded crashes. As
libfeedback was not compiled with embedded, we had 2 notions of THD,
with different number of members. When calling inline functions defined in
sql_class.h, the functions were defined for 1 THD but called on an
object that is different. This resulted in erroneous data being returned
and shortly after, a crash within the alloc_query() function.

Recompile the feedback plugin for the embedded server specifically to
not have such symbol conflicts.