Some comment, doc and bug fixes.

Some comment, doc and bug fixes.
(ps-print-version): New version number (3.06) and doc fix.
(ps-print-only-one-header, ps-font-type): New var.
(ps-font-info-database): Better font database management.
(ps-error-scale-font, ps-select-header-font): Funs eliminated.
(ps-font, ps-font-bold, ps-font-italic, ps-font-bold-italic)
(ps-avg-char-width, ps-space-width, ps-line-height)
(ps-header-font, ps-header-title-font, ps-header-line-height)
(ps-header-title-line-height): Vars eliminated.
(ps-font-list, ps-font, ps-fonts, ps-font-number, ps-line-height)
(ps-title-line-height, ps-space-width, ps-avg-char-width,): New funs.
(ps-print-prologue-1): Adjust PostScript programming.
(ps-color-format): Doc indentation.
(ps-print-hook, ps-print-begin-page-hook, ps-print-begin-column-hook):
New hook vars.
(ps-spool-without-faces, ps-spool-with-faces): Run hook var.
(ps-line-lengths-internal, ps-nb-pages, ps-select-font)
(ps-get-page-dimensions, ps-begin-file, ps-end-file, ps-header-page)
(ps-begin-page, ps-dummy-page, ps-next-line, ps-continue-line)
(ps-basic-plot-string, ps-basic-plot-whitespace, ps-plot-region)
(ps-control-character, ps-color-values, ps-generate): Adjust programming.
(ps-page-number): New macro.
(ps-plot-with-face, ps-generate-postscript-with-faces): Fix invisible
text printing.