Log Message:
libnotify: Readd `introspection' option and install gtk-doc for `doc' option

- Readd introspection option (enabled by default) like it was present in
  previous libnotify version.
- gtk-doc is probably a "bigger" tool dependency than xmlto, make it \ 
part of
  the `doc' option (this also make gtk-doc no longer a tool dependency by
  default).

Bump PKGREVISION

Discussed and thanks to <wiz>!