Make landscape layout with geometry package rather than a PostScript special.

Make landscape layout with geometry package rather than a PostScript special.

* lisp/calendar/cal-tex.el (cal-tex-preamble): Make 12pt the
default class option.
(cal-tex-year, cal-tex-cursor-month-landscape): Pass landscape
request to `cal-tex-insert-preamble' function call within the
class option string.
(cal-tex-cursor-month): Don't pass any longer "12pt" argument
to `cal-tex-insert-preamble' function, as it is default.
(cal-tex-insert-preamble): Suppress landscape and size
argument, and replace them by a class-options string
argument. Do not insert any longer "\special{landscape}" in
case of landscape layout, as the job is made by the geometry
package.