Quartz Brews: Add :alt keyword to depends_on
So that `brew-tap` (the external command version) can properly resolve
New Formula: Inkscape
Added a formula for an Inkscape build that uses Quartz instead of X11 as a
A bit rough around the edges---segfaults when quitting.
New Formulae for native GTK+ stack
These all build keg_only to keep them from interfearing witht the official GTK+