into screen_ctx and start passing screen_ctx around to in order get rid
of Curscreen; fixup per-screen config colors the same way.
diff mostly from oga@, with a bit harsher reaction to the state of screen_ctx.
"please commit" oga@
using Xft(3), use it to select the font color as well instead of trying
to build one; properly allocate and free colors at-will, e.g. we now
have configurable colors.
feedback and ok's todd@ and oga@
