Fix documentation installation directory
Fix documentation installation directory

https://bugzilla.gnome.org/show_bug.cgi?id=657054

thiblahute/pygobject,jdahlin/pygobject,sfeltman/pygobject,jdahlin/pygobject,pexip/pygobject,davibe/pygobject,choeger/pygobject-cmake,davidmalcolm/pygobject,davibe/pygobject,davidmalcolm/pygobject,MathieuDuponchelle/pygobject,GNOME/pygobject,davidmalcolm/pygobject,MathieuDuponchelle/pygobject,pexip/pygobject,GNOME/pygobject,GNOME/pygobject,jdahlin/pygobject,sfeltman/pygobject,choeger/pygobject-cmake,thiblahute/pygobject,thiblahute/pygobject,MathieuDuponchelle/pygobject,choeger/pygobject-cmake,davibe/pygobject,davibe/pygobject,sfeltman/pygobject,pexip/pygobject