Fixed that internal temporary tables are not waiting for freed disk space.

Other things:
- 'kill id' will now kill a query waiting for free disk space instantly.
  Before it could take up to 60 seconds for the kill would be noticed.
- Fixed that sorting one index is not using MY_WAIT_IF_FULL for temp files.
- Fixed bug where share->write_flag set MY_WAIT_IF_FULL for temp files.

It is quite hard to do a test case for this. Instead I tested all
combinations interactively.