Fix appimage build of mimetreeparser

* Makefile.am (EXTRA_DIST): Add patch.
* patches-appimage/mimetreeparser/
0001-Use-GpgmeppConfig-instead-of-FindGpgme.patch.

This replaces the FindGPGME in Mimetreeparser by using
the GpgMEppConfig. There will a MR for this of course but for
me it was easiest to test the build first with a patch here.