GParameter deprecation throws a lot of warnings

[pkern]

libinfinity uses GParameter in its API and that has been deprecated in GLib 2.54. That throws a lot of deprecation warnings in software using libinfinity (aka Gobby) and during build. I think it'd be useful to go with G_GNUC_BEGIN/END_IGNORE_DEPRECATIONS, given that it's not going away in GLib 2 anyway.

[pkern]

Obviously the callers will still use GParameter locally and get deprecation warnings for that, so I guess more fixing is in order here.