Include enclosures in ttrss feeds

Prior to this change TinyTinyRSS feeds with attached media such as MP3 or OGG
files could not be added to the podcast queue. Now the first attachment appears
as the "Podcast Download URL" in the article view.
Merge branch 'master' of git://github.com/richq/newsbeuter into richq-master

Conflicts:
	src/ttrss_api.cpp
Merge branch 'master' of github.com:akrennmair/newsbeuter