In 32ac7c75 the behavior of
FcConfigAppFontAddFile/Dir() were changed to return false
if not fonts were found.  While this is welldefined and useful
for AddFile(), it's quite problematic for AddDir().  For example,
if the directory is empty, is that a failure or success?  Worse,
the false value from AddDir() was being propagated all the way
to FcInit() returning false now.  This only happened upon memory
allocation failure before, and some clients assert that FcInit()
is successful.

With this change, AddDir() is reverted back to what it was.
AddFont() change (which was actually in fcdir.c) from the original
commit is left in.