Footers implementation. Doc Fix.

Footers implementation.  Doc Fix.
(ps-print-version): New version number (6.5.1).
(ps-header-frame-alist): New customization var for header frame
properties.
(ps-line-number-color): New customization var for line number color.
(ps-footer-offset, ps-footer-line-pad, ps-print-footer)
(ps-print-footer-frame, ps-footer-frame-alist, ps-footer-lines)
(ps-footer-font-family, ps-footer-font-size, ps-left-footer)
(ps-right-footer): New customization vars for footers.
(ps-footer-pad, ps-footer-font-size-internal): New internal vars for
footers.
(ps-setup, ps-get-page-dimensions, ps-generate-header-line)
(ps-generate-header, ps-begin-file, ps-begin-job, ps-begin-page): Code
fix.
(ps-prologue-file): Indentation fix.
(ps-print-quote): Fun eliminated.
(ps-value, ps-get, ps-put, ps-del): New funs for alist handling.
(ps-output-frame-properties): New fun.
(ps-fonts, ps-font-number, ps-rgb-color, ps-end-page, ps-next-page)
(ps-skip-newline): Replace defun by defsubst.