font/basicfont: new package for a basic font face.

The key feature is that its data is entirely self-contained and does not
require loading from separate files.

Change-Id: I4ef72b52cde93597be89dcfd55659f418c6cab23
Reviewed-on: https://go-review.googlesource.com/14486
Reviewed-by: Rob Pike <r@golang.org>
3 files changed