Also, fixing a bug in STR_TO_DATE(). It erroneously returned
error in strict mode for dates like '0000-01-01'
(zero year, but non-zero month and day).

According to the manual:
- NO_ZERO_DATE disallows 0000-00-00 (all date parts are zeros)
- NO_ZERO_IN_DATE disallows zero month (YYYY-00-DD) or day (YYYY-MM-00).

0000-01-01 is a valid date, even in strict mode.


modified:
  mysql-test/r/func_time.result
  mysql-test/r/strict.result
  mysql-test/t/func_time.test
  mysql-test/t/strict.test
  sql/item_timefunc.cc
  sql/sql_time.h
pending merges:
  Alexander Barkov 2013-06-17 MDEV-4635 Crash in UNIX_TIMESTAMP(STR_TO_DAT...