Update libgepub to version 0.7.3 / rev 9 via SR 1267618
https://build.opensuse.org/request/show/1267618
by user dimstar + anag_factory
- Update to version 0.7.3:
+ Fix integer overflow in gepub-archive
+ Install missing config.h and gepub-widget.h (forwarded request 1267610 from iznogood)