Fixed confusing error message from the storage engine when
it fails to open underlying table. The error message is issued
when a table is _opened_ (not when it is created).


myisammrg/myrg_open.c:
  Set my_errno to HA_ERR_WRONG_MRG_TABLE_DEF if attempt to open
  underlying table failed.
mysql-test/r/merge.result:
  A test case for bug#10974.
mysql-test/r/repair.result:
  Fixed a test case according to patch for bug#10974.
mysql-test/t/merge.test:
  A test case for bug#10974.
sql/share/english/errmsg.txt:
  Better error message if we fail to open underlying table.
sql/table.cc:
  Report error from handler with print_error instead of frm_error. This
  fixes confusing error message from the handler. Actually this is
  backported from 5.0.