CHECK TABLE against ARCHIVE table may falsely report table corruption,
or cause server crash.

Fixed by using proper buffer for CHECK TABLE.

Affects both 5.0 and 5.1.


mysql-test/r/archive.result:
  A test case for BUG#28916.
mysql-test/t/archive.test:
  A test case for BUG#28916.
sql/ha_archive.cc:
  We call Field::get_length() from get_row(). Field::get_length() assumes
  that the row was read into table->record[0] buffer, which is not the
  case when we check a table. As a result we get wrongly initialized
  blob length.
  
  Use table->record[0] as record buffer for check table instead.