bdftopcf: add recipe

The bdftopcf tool is necessary to build the core X fonts, which ship in
BDF format.  Adapted from a recipe in OE-Classic and from an earlier
mailing list post by Trevor Woerner.

Signed-off-by: Ben Shelton <ben.shelton@ni.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>