(ps-print-prologue-1): Fix bug in postscript comment lines.

(ps-print-prologue-1): Fix bug in postscript comment lines.
(ps-nb-pages): Call ps-setup _before_ switching to the other
buffer, because of buffer variables.

Major rewrite.
(ps-page-dimensions-database, ps-paper-type): Replace the
following global variables:
(ps-a4-page-height, ps-a4-page-width, ps-legal-page-height,
ps-legal-page-width, ps-letter-page-height, ps-letter-page-width,
ps-pages-alist, ps-page-dimensions): Variables deleted.
(ps-page-height-i, ps-page-width-i): Variables deleted.
(ps-print-prologue): Variable deleted.
(ps-print-prologue-1, ps-print-prologue-2): New variables.
Major rewrite of the postscript code to handle landscape mode,
multiple columns and new font management.
(ps-landscape-mode, ps-number-of-columns, ps-inter-column): New
variables.
Add landscape mode and multiple columns with interspacing.
(ps-font-info-database, ps-font-family, ps-font-size,
ps-header-font-family, ps-header-font-size, ps-header-title-font,
ps-header-title-font-size): New variables.
New font management interface.
(ps-header-line-pad, ps-header-offset): New variables.
(ps-header-font, ps-landscape-page-height): New internal variables.
(ps-top-margin): Change its semantics.  It is now really the top
margin, not anymore twice the top margin.
(/ReportAllFontInfo):  New postscript function to get all the font
families of the printer.
(ps-setup): New function.
(ps-line-lengths, ps-nb-pages-buffer, ps-nb-pages-region): New
utility functions.
(ps-page-dimensions-get-width, ps-page-dimensions-get-height): New macros.
(/HeaderOffset): Fix bug with /PrintStartY.
(/SetHeaderLines): Fix bug.