A lot of comment and doc fixes.

A lot of comment and doc fixes.
Replace: 'nil by nil, '() by nil, 't by t.

(ps-print-version): New version number (3.05).
(ps-zebra-stripe, ps-number-of-zebra, ps-line-number)
(ps-print-background-image, ps-print-background-text): New variables
to customize zebra stripes, line number, image background and text
background features, respectively.
(ps-adobe-tag): Tagged to PostScript level 3.
(ps-print-buffer, ps-print-buffer-with-faces)
(ps-print-region, ps-print-region-with-faces)
(ps-spool-buffer, ps-spool-buffer-with-faces)
(ps-spool-region, ps-spool-region-with-faces): Call more primitive
functions for PostScript printing (functions below).
(ps-print-with-faces, ps-print-without-faces)
(ps-spool-with-faces, ps-spool-without-faces): More primitive
functions for PostScript printing.
(ps-line-lengths, ps-nb-pages-buffer, ps-nb-pages-region)
(ps-line-lengths-internal, ps-nb-pages): Doc fixes.
(ps-print-prologue-1): a lot of PostScript programming:
/dobackgroundstring, /dounderline, /UL: Postscript functions deleted.
/reencodeFontISO, /F, /BG, /HL, /W, /S, /BeginDSCPage, /BeginPage,
/EndPage: adjusted for new effects (outline, shadow, etc).
/PLN, /EF, /Hline, /doBox, /doRect, /doShadow, /doOutline,
/FillBgColor, /doLineNumber, /printZebra, /doColumnZebra,
/doZebra, /BeginBackImage, /EndBackImage, /ShowBackText: New procedures.
(ps-current-underline-p, ps-set-underline): Var and fn deleted.
(ps-showline-count, ps-background-pages, ps-background-all-pages)
(ps-background-text-count, ps-background-image-count): New variables.
(ps-header-font, ps-header-title-font)
(ps-header-line-height, ps-header-title-line-height)
(ps-landscape-page-height): Set initial value to nil.
(ps-print-face-extension-alist, ps-print-face-map-alist):
New variables for face remapping.
(ps-new-faces, ps-extend-face-list, ps-extend-face):
New functions for face remapping.
(ps-override-list, ps-extension-to-bit-face)
(ps-extension-to-screen-face, ps-extension-bit)
(ps-initialize-faces, ps-map-font-lock, ps-screen-to-bit-face):
New internal functions for face remapping.
(ps-get-page-dimensions): Fix error message.
(ps-insert-file): Doc fix and programming enhancement.
(ps-begin-file, ps-end-file, ps-get-buffer-name, ps-begin-page)
(ps-next-line, ps-plot-region, ps-face-attributes)
(ps-face-attribute-list, ps-plot-with-face)
(ps-generate-postscript-with-faces): Handle new output features.
(ps-generate): save-excursion inserted to return back point at
position before calling ps-print.
(ps-do-spool): Access dos-ps-printer variable through symbol-value.
(ps-prsc, ps-c-prsc, ps-s-prsc): Use backquote.
(ps-basic-plot-whitespace, ps-emacs-face-kind-p): Internal blank
line eliminated.
(ps-float-format, ps-current-effect): New internal variables.
(ps-output-list, ps-count-lines, ps-background-pages)
(ps-get-boundingbox, ps-float-format, ps-background-text)
(ps-background-image, ps-background, ps-header-height)
(ps-get-face): New internal functions.
(ps-control-character): Handle control characters.
(ps-gnus-print-article-from-summary): Updated for Gnus 5.
(ps-jack-setup): Replace 'nil by nil, 't by t.