Post merge changes
sql_yacc.yy:
  Post merge changes
sql_select.cc:
  Fixed bugs #12101, #12102: wrong calculation of not_null_tables()
   for some expressions (post merge changes).
   The function add_key_fields() is modified. There cannot be NOT before
   BETWEEN/IN anymore. Rather Item_func_between/in objects can represent
   now [NOT]BETWEEN/IN expressions.