mysql-test/r/sp-error.result:
  Results for the test case for BUG#13037.
mysql-test/t/sp-error.test:
  Test case for BUG#13037.
sql/sql_base.cc:
  Polishing: use constant.
sql/sql_class.cc:
  Reset THD::where in THD::cleanup_after_query();
  Polishing: use the constant (THD::DEFAULT_WHERE).
sql/sql_class.h:
  Introduce a constant for the default value of THD::where.