util._matcher: unify pattern normalization
This should fix
issue347.
It also highlights one issue with the directory walking code when
you have an --include pattern that matches the end of a filename.
This is fixed by the next patch.
adding dir/bar
adding foo
dir/bar
foo
adding dir/bar_2
adding foo_2
dir/bar_2
foo_2
adding a
adding c
adding b
adding d
removing a
removing c
recording removal of a as rename to b (100% similar)