(Bug #2694)


innobase/include/srv0srv.h:
  Add srv_fatal_semaphore_wait_threshold
innobase/include/sync0arr.h:
  Improve comment of sync_array_print_long_waits()
innobase/row/row0mysql.c:
  Lengthen the srv_fatal_semaphore_wait_threshold by 2 hours during
  CHECK TABLE
innobase/srv/srv0srv.c:
  Add srv_fatal_semaphore_wait_threshold
innobase/sync/sync0arr.c:
  Improve comment of sync_array_print_long_waits().
  Replace the fixed timeout of 600 seconds with
  srv_fatal_semaphore_wait_threshold.