Use (defvar <foo>) where applicable.

Use (defvar <foo>) where applicable.
(ps-print-emacs-type): Remove.
(ps-x-frame-property, ps-e-frame-parameter): Remove.
(ps-frame-parameter): Align its call-convention with frame-parameter.
(ps-begin-job): Adjust calls to it appropriately.
(ps-setup): Don't print ps-print-emacs-type.
(ps-e-find-composition, ps-mark-active-p, ps-color-device):
Define in such a way that it's obvious that it's defined.
(ps-prsc, ps-c-prsc, ps-s-prsc): Remove.
(ps-rmail-mode-hook, ps-vm-mode-hook, ps-gnus-summary-setup)
(ps-jts-ps-setup): Use flavor-neutral syntax instead.