(bdf-find-font-info): New function, looks for the first readable
file from a list of alternatives.
(bdf-get-bitmaps, bdf-generate-font): Call bdf-find-font-info
instead of bdf-get-font-info.
(bdf-generate-glyphs): If font-name is a cons cell, pass its car
to ps-mule-generate-bitmap-glyph.