Removed the ability to cache queries containing "UUID()".


mysql-test/r/query_cache.result:
  Added test to ensure "select UUID(), a from t1" is different each time.
mysql-test/t/query_cache.test:
  Added test to ensure "select UUID(), a from t1" is different each time.
sql/item_create.cc:
  Removed the ability to cache queries with UUID().