.gitignore: Add a few more autotools generated files

Newer autoconf/automake copy a script called 'compile' and a
'test-driver', which should not be committed, so they're best ignored.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
Merge pull request #8 from algernon/f/gitignore-update

.gitignore: Add a few more autotools generated files