Cut down on boilerplate by using the (no longer that) new helper
macros. We don't care about breaking ABI in private libraries, so
use G_DECLARE_FINAL_TYPE even where the class struct used to be
exposed in the header, except for types we inherit from ourselves
(obviously) or where the class exposes any vfuncs (where changes
could affect inheritance in extensions).
Add a "gicon" property so that a GIcon can be used instead of an
icon name, while still getting icon recoloring from the theme.
Also include a compatibility wrapper in libshell until GJS has
support for interface static methods.
https://bugzilla.gnome.org/show_bug.cgi?id=622451
Make StIcon compile and work in St.
Changes:
* ::icon-type and st_icon_set_icon_type are added to allow
specifying SYMBOLIC/FULLCOLOR for an icon.
* Ability to set the icon name from the theme is removed; it
wouldn't easily fit into our framework and two levels of
abstraction between code and image doesn't seem that useful.
* size CSS property is renamed from x-st-icon-size to icon-size
to correspond to what we are doing elsewhere.
* CSS and property based icon sizing are cleanly layered - if
you set the icon-size property, the CSS size is ignored.
* Add a simple JS test of StIcon.
https://bugzilla.gnome.org/show_bug.cgi?id=633865
