graphics/gexiv2: update to 0.12.0

http://ftp.acc.umu.se/pub/gnome/sources/gexiv2/0.11/gexiv2-0.11.0.news
http://ftp.acc.umu.se/pub/gnome/sources/gexiv2/0.12/gexiv2-0.12.0.news

This includes/obsoletes our patches.
The vala api of gexiv2 changed, this needed to be reflected in
graphics/shotwell (no other port seems to use the vala interface).