Removed random failures from test suite

mysql-test/extra/rpl_tests/rpl_insert_id_pk.test:
  Make test predicatable.
mysql-test/include/maria_empty_logs.inc:
  We can't use 'Threads_connected' for syncronization, as the 'check_warnings' thread that just quit may still be counted in 'Threads_connected'
  Now we just wait until MySQLD answers again, which should be good enough for our purposes
mysql-test/suite/binlog/r/binlog_index.result:
  Updated results file
mysql-test/suite/binlog/t/binlog_index-master.opt:
  Added option file to not get stack traces in .err file.
mysql-test/suite/binlog/t/binlog_index.test:
  Added 'flush tables' to remove warning about crashed suppression file from logs
mysql-test/suite/pbxt/r/multi_statement.result:
  Updated results
mysql-test/suite/pbxt/t/multi_statement-master.opt:
  Added options so that slow query testing makes sense
sql/events.cc:
  Don't write Event Scheduler startup message if warnings are turned off.
sql/handler.cc:
  Removed compiler warning
sql/log.cc:
  Removed compiler warning
sql/mysqld.cc:
  Added option 'test-expect-abort'; If this is set, we don't write message to log in case of 'DBUG_ABORT'.
  (Gives us smaller, easier to read log files)
sql/set_var.cc:
  Removed compiler warning
sql/slave.cc:
  Removed compiler warning
sql/sql_plugin.cc:
  Don't write warnings about disabled plugin if using --log_warnings=0
storage/xtradb/include/ut0lst.h:
  Removed compiler warning
support-files/compiler_warnings.supp:
  Supress warning from xtradb