BUG#18198: Many strange partition functions were allowed, now only strictly allowed functions are ok


mysql-test/r/partition_error.result:
  New test cases
mysql-test/t/partition_error.test:
  New test cases
sql/item.h:
  Added method check_partition_func_processor for check if item tree is valid
sql/item_cmpfunc.h:
  Added method check_partition_func_processor for check if item tree is valid
sql/item_func.h:
  Added method check_partition_func_processor for check if item tree is valid
sql/item_strfunc.h:
  Added method check_partition_func_processor for check if item tree is valid
sql/item_timefunc.h:
  Added method check_partition_func_processor for check if item tree is valid
sql/item_xmlfunc.h:
  Added method check_partition_func_processor for check if item tree is valid