Simplify doc/misc/Makefile.in with GNU Make features

Simplify doc/misc/Makefile.in with GNU Make features

* doc/misc/Makefile.in (mkinfodir): Remove.
(${buildinfodir}): Generate using an order-only prerequisite.
(.dvi.ps): Replace with pattern rule.
($INFO_TARGETS): Mark as PHONY.
(${buildinfodir}): New rule.
(EXTRA_OPTS, need_emacsver, need_emacsver_prefix): New variables.
(${buildinfodir}/%.info, %.dvi, %.pdf, %.html, %.ps):
New pattern rules, replacing numerous previous explicit rules.
(info_template): New definition.
(gnus.dvi, gnus.pdf): Use distinct intermediate files.
(mostlyclean): Adjust for above gnus change.