update .gitignore

Add build-aux/test-driver to .gitignore.

Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
configure.ac: Don't let pthread check depend on OS

Don't check the operating system environment to detect the correct
linker flags for using the POSIX thread library.
Merge branch 'check-disk-thread' into pu

* check-disk-thread:
  configure.ac: Don't let pthread check depend on OS
  check_disk: Seperate declarations from code
  check_disk: Remove unused status variable
  check_disk: Fix pthread start routine type
  Don't let check_disk hang on hanging filesystems