shiny/font/plan9font: implement ParseFont.

Also delete font.MultiFace. We can resurrect a font.MultiFace type if we
need it in the future, but for now, it's simpler if it lives in the
plan9font package.

Change-Id: I1493b47696c323424e7d91cb7fac15505bfdd023
Reviewed-on: https://go-review.googlesource.com/13520
Reviewed-by: Rob Pike <r@golang.org>
3 files changed