.gitignore: Add *~

In particular, although emacs generally doesn't generate ~ backup
files when working in a git tree, autoreconf does generate
config.h.in~, which should be ignored.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

xf86-input-mtrack (0.3.1-1) unstable; urgency=medium

  * Upload to unstable.
  * Fix debian/copyright format.

# imported from the archive