File name changed from bdf.el. Provide ps-bdf

File name changed from bdf.el.  Provide ps-bdf
instead of bdf.

Require ps-mule instead of ps-print.
(bdf-directory-list): Add autoload cookie.

Programming uniformization and little code improvement.
(bdf-search-and-read): New fun.
(bdf-write-cache, bdf-initialize, bdf-info-absolute-path)
(bdf-info-mod-time, bdf-info-size, bdf-info-font-bounding-box)
(bdf-info-relative-compose, bdf-info-baseline-offset)
(bdf-info-code-range, bdf-info-maxlen, bdf-info-offset-vector)
(bdf-read-bitmap, bdf-get-bitmaps): Programming uniformization.
(bdf-expand-file-name, bdf-file-newer-than-time, bdf-find-file)
(bdf-read-cache, bdf-read-font-info, bdf-generate-glyphs): Little code
improvement.