This adds a TIME_MS column to SHOW FULL PROCESSLIST and
INFORMATION_SCHEMA.PROCESSLIST that works like the TIME column, but
in units of milliseconds with microsecond precision.

Note that this also changes behaviour of the existing TIME column. In
the MySQL server, the TIME column changes when a thread sets @TIMESTAMP.
This is contrary to documentation and also potentially confusing, so
could in any case be considered a bug. With this patch, to ensure
consistency between TIME and TIME_MS, setting @TIMESTAMP has no effect
on either value.

Add a test case for the TIME and TIME_MS columns.
Update existing test cases for changed behaviour.

Author: Percona
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>


mysql-test/r/create.result:
  Result file update.
mysql-test/r/information_schema.result:
  Add test case.
  Result file update (changed behaviour).
mysql-test/t/information_schema.test:
  Add test case.
  Adjust test case for changed behaviour.
mysql-test/t/not_embedded_server.test:
  Update (commented-out) test case for newly added column.
sql/sql_show.cc:
  Merge Percona microsec_process patch into MariaDB.