- Exclude RAW thumbnailer on Leap 15.5+ as well

- Allow building against libgepub-0.7 (boo#1203644):
+ Adjust BuildRequires to work with libgepub-0.6 or libgepub-0.7.
+ Replace libgepub-0.6 occurences in configure script with
libgepub-0.7 when libgepub 0.7 is present.

- Update to version 4.16.1
* gst-thumbnailer: Add mime type check (gxo#xfce/tumbler#65)
* desktop-thumbnailer: Guard against null path
* Fix typo in gthread version (gxo#xfce/tumbler!14)

- Exclude RAW thumbnailer on Tumbleweed only to fix build on Leap

- RelMgr override: do not package raw thumbnailer, as tumbler does
not yet support openraw 0.3.