PostScript programming fix for ghostview, doc fix.

PostScript programming fix for ghostview, doc fix.
(ps-print-version): New version number (5.1.3).
(ps-begin-file, ps-begin-job, ps-set-color, ps-do-despool, ps-setup)
(ps-insert-file, ps-output-boolean, ps-plot-with-face)
(ps-generate-postscript-with-faces): Code fix.
(ps-color-values): XEmacs compatibility.
(ps-print-background-image, ps-print-background-text, ps-printer-name)
(ps-default-fg, ps-default-bg): Adjust customization.
(ps-zebra-color): Adjust customization, renaming old ps-zebra-gray var.
(ps-color-scale): Renaming old ps-color-value fun.
(ps-print-headers): Replace ps-print-header group to avoid conflict
with ps-print-header variable.
(ps-print-miscellany): New group.
(ps-format-color, ps-rgb-color): New funs.
(ps-default-foreground): New var.
(ps-printer-name-option): New const.