media-libs/libchamplain: fix gtk-doc, other fixes and touchups

media-libs/libchamplain: fix gtk-doc, other fixes and touchups

* Fix LICENSE from LGPL-2 to LGPL-2.1+.
* Fix USE=gtk-doc to always be honored (implicitly disabled upstream
  if gtk widgetry is disabled) and actually show up in devhelp.
* Add missing meson minimum version requirement - requires 0.49.0,
  but meson.eclass only guarantees 0.48.2 at this point.
* Fix EAPI-7 bump to actually be an EAPI-7 port by properly using
  DEPEND and BDEPEND.
* Use emesonargs array to be able to comment options on the relevant
  line.
* Add longdescription to metadata.
* Sort deps and options in occurrences order for easier review on
  future bumps.
* Depend on >=gobject-introspection-1.54 to ensure compat with meson.

Package-Manager: Portage-2.3.52, Repoman-2.3.12
Signed-off-by: Mart Raudsepp <leio@gentoo.org>