Fix bug: if ^L is the very first buffer character,

Fix bug: if ^L is the very first buffer character,
ps-print crashes.  New feature: page selection for printing.  Create
raw-text-unix coding system for XEmacs.  Doc fix.
(ps-print-version): New version number (5.2.3).
(ps-plot-region): Bug fix.
(ps-setup, ps-init-output-queue, ps-output, ps-begin-job, ps-end-file)
(ps-header-sheet, ps-generate, ps-end-job): Code fix.
(ps-restore-selected-pages, ps-selected-pages, ps-print-page-p): New
funs.
(ps-selected-pages, ps-last-selected-pages, ps-first-page)
(ps-last-page): New vars.