The cause of the crash was that test was setting
aria_sort_buffer_size to MAX_LONG_LONG, which caused an overflow in
my_malloc() when trying to allocate the buffer + 8 bytes.

Fixed by reducing max size of sort_buffer for Aria and MyISAM

Other things:
- Added code in maria_repair_parallell() to not allocate a big sort buffer
  for small files.
- Updated size of minumim sort buffer in Aria