mysql-test/r/func_misc.result:
  Add new results
mysql-test/t/func_misc.test:
  Add new regression test.
sql/item_create.cc:
  When SLEEP() is used, mark the statement as uncacheable.
sql/item_func.h:
  Flag SLEEP() as not constant, and set RAND_TABLE_BIT so that it is
  always evaluated.