Location: Add methods, properties and vfuncs

	* Create champlain_vfuncs.defs with Location vfuncs.
	* champlain.defs: Include champlain_vfuncs.defs
	* generate_extra_defs_libchamplain.cc: Add
	CHAMPLAIN_TYPE_LOCATION.
	* champlain_signals.defs: Regenerate to include Location
	properties.
	* Add set_location(), get_latitude(), get_longitude() methods.
	* Add ::latitude, ::longitude properties.