Couple of small fixes following buildbot testing.

Some GTID test cases were using include/wait_condition.inc with a
condition like SELECT COUNT(*)=4 FROM t1 to wait for the slave to
catch up with the master. This causes races and test failures, as the
changes to the tables become visible at the COMMIT of the SQL thread
(or even before in case of MyISAM), but the changes to
@@gtid_slave_pos only become visible a little bit after the COMMIT.

Now that we have MASTER_GTID_WAIT(), just use that to sync up in a
GTID-friendly way, wrapped in nice include/save_master_gtid.inc and
include/sync_with_master_gtid.inc scripts.

MASTER_GTID_WAIT() is similar to MASTER_POS_WAIT(), but works with a
GTID position rather than an old-style filename/offset.

@@LAST_GTID gives the GTID assigned to the last transaction written
into the binlog.

Together, the two can be used by applications to obtain the GTID of
an update on the master, and then do a MASTER_GTID_WAIT() for that
position on any read slave where it is important to get results that
are caught up with the master at least to the point of the update.

The implementation of MASTER_GTID_WAIT() is implemented in a way
that tries to minimise the performance impact on the SQL threads,
even in the presense of many waiters on single GTID positions (as
from @@LAST_GTID).

 SET(CMAKE_INCLUDE_DIRECTORIES_PROJECT_BEFORE ON)
to find header files from the bundled libraries
(jemalloc, yassl, readline, pcre, etc)
before the ones installed in the system.

There are some places in parallel replication where transactions wait
for one another. Make sure those waits are killable by the (super)user.

Upon kill, unfinished transactions will be rolled back and the SQL thread
stops with an error.

Add a number of test cases to test the different cases. Also fix some
existing bugs found by those tests.

Add another test case. This one for killing a query that is waiting
for a prior commit, when --log-slave-updates=0 (in this case the
wait happens in different code from --log-slave-updates=1).

Add another test case. This one for killing the SQL driver thread while it is
waiting for room in the list of events queued for a worker thread.

Fix bugs found:

 - Several memory leaks in various error cases.

 - SQL error code was not set (for SHOW SLAVE STATUS etc.) when killed.

Fixing "/*100000 ...*/" comments (i.e. MySQL style with 6-digits),
which were unintentionally broken in the MDEV-5009 patch.

modified:
  mysql-test/r/comments.result
  mysql-test/t/comments.test
  sql/sql_lex.cc

  
Add another test case. This one for killing a worker while its transaction is
waiting to start until the previous transaction has committed.

Fix setting reading_or_writing to 0 in worker threads so SHOW SLAVE STATUS can
show something more useful than "Reading from net".

Add another test case.

Fixed a wrong assertion.

Add another test case.

Fix bug found: When one thread aborts, another thread might
wrongly advance the relay log position too far, causing the
fauling transaction to be skipped and thus lost upon
restarting the SQL thread after the failure.

backporting from the main 10.0

modified:
  mysql-test/r/func_like.result
  mysql-test/t/func_like.test
  sql/item_cmpfunc.cc

Fix locking bug / race introduced by previous patch: If we
bail out of next_event() due to kill, there was a small window
where we could exit without rli->data_lock held, causing an
unlock-twice bug.

This test needs at least 320M for tokudb-max-lock-memory.
Normally tokudb-max-lock-memory is auto-sized to be 1/16th
of the available RAM size, and many our test VMs have 4G of RAM.

Do not calculate selectivity of conditions for the tables of the information schema.

Add a test case for killing a waiting query in parallel replication.

Fix several bugs found:

 - We should not wakeup_subsequent_commits() in ha_rollback_trans(), since we
   do not know the right wakeup_error() to give.

 - When a wait_for_prior_commit() is killed, we must unregister from the
   waitee so we do not race and get an extra (non-kill) wakeup.

 - We need to deal with error propagation correctly in queue_for_group_commit
   when one thread is killed.

 - Fix one locking issue in queue_for_group_commit(), we could unlock the
   waitee lock too early and this end up processing wakeup() with insufficient
   locking.

 - Fix Xid_log_event::do_apply_event; if commit fails it must not update the
   in-memory @@gtid_slave_pos state.

 - Fix and cleanup some things in the rpl_parallel.cc error handling.

 - Add a missing check for killed in the slave sql driver thread, to avoid a
   race.

The fix for bug #27937 was incomplete: it did not handle correctly the queries
containing UNION with global ORDER BY in subselects.

(better to have an address in the output than ??:0)

(PLUGIN_VAR_MEMALLOC is 0x8000 and cannot be saved in a char as such)"

https://github.com/Tokutek/ft-engine/issues/153

don't reset interrupted_query after sending the KILL signal, otherwise
the client won't know it has to stop fetching and printing the data.

a memory leak in save_index() first seen in the test case for mdev-5382.

A couple of more parallel replication waits made killable.

When marking used columns the function find_field_in_table_ref() erroneously
called the walk method for the real item behind a view/derived table field
with the second parameter set to TRUE.
This erroneous code was introduced in 2006. 

Make wait_for_prior_commit killable, and handle the error if
killed.

Correct processing of view/derived with no tables added.

"Conditional jump or move depends on uninitialised"
in Item_time_typecast::get_date.

Adding "null_value" into the debug assert condition.

modified:
  mysql-test/r/func_time.result
  mysql-test/t/func_time.test
  sql-common/my_time.c
  sql/item_func.h
  sql/item_timefunc.cc
  sql/mysql_priv.h
  sql/time.cc