app-misc/geoclue: 2.5 series packaging fixes, unmask

app-misc/geoclue: 2.5 series packaging fixes, unmask

* Enable demo-agent as in 2.4.13, as it's the only known agent
  available for non-GNOME for actually having a geoclue service
  responding on other desktops than GNOME
* Rewrite optional vapi patch to not need sedding
* Port to EAPI-7
* Add missing REQUIRED_USE="vala? ( introspection )"
* Drop unnecessary bogus VALA_MIN_API_VERSION
* Drop unnecessary gnome.org.eclass inherit
* Fix LICENSE
* Fix gtk-doc dep to be conditional to USE=gtk-doc, add missing
  docbook-xml-dtd dep
* Reorder emesonargs to meson_options.txt order for easier
  (future) review and drop unnecessary backslashes at EOLs
* Various other touchups
* Unmask it now together with newer xdg-desktop-portal, as it's
  been reviewed now

Closes: https://bugs.gentoo.org/678814
Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: Mart Raudsepp <leio@gentoo.org>