Give info files the .info extension

Give info files the .info extension

Ref http://lists.gnu.org/archive/html/emacs-devel/2012-04/msg00354.html

* configure.in (INFO_EXT, INFO_OPTS): New output variables.

* doc/emacs/Makefile.in (INFO_EXT, INFO_OPTS): New, set by configure.
(info, infoclean): Use $INFO_EXT.
($(infodir)/emacs$(INFO_EXT)): Use $INFO_EXT and $INFO_OPT.
* doc/emacs/makefile.w32-in (INFO_EXT, INFO_OPTS): New.
(INFO_TARGETS): Use $INFO_EXT.
($(infodir)/emacs$(INFO_EXT)): Use $INFO_EXT and $INFO_OPT, and -o.

* doc/lispintro/Makefile.in (INFO_EXT, INFO_OPTS): New, set by configure.
(info, infoclean): Use $INFO_EXT.
(${infodir}/eintr$(INFO_EXT)): Use $INFO_EXT and $INFO_OPT.
* doc/lispintro/makefile.w32-in (INFO_EXT, INFO_OPTS): New.
(INFO_TARGETS, clean): Use $INFO_EXT.
($(infodir)/eintr$(INFO_EXT)): Use $INFO_EXT and $INFO_OPT.

* doc/lispref/Makefile.in (INFO_EXT, INFO_OPTS): New, set by configure.
(info, infoclean): Use $INFO_EXT.
($(infodir)/elisp$(INFO_EXT)): Use $INFO_EXT and $INFO_OPT.
* doc/lispref/makefile.w32-in (INFO_EXT, INFO_OPTS): New.
(info, maintainer-clean): Use $INFO_EXT.
($(infodir)/elisp$(INFO_EXT)): Use $INFO_EXT and $INFO_OPT.

* doc/misc/Makefile.in (INFO_EXT, INFO_OPTS): New, set by configure.
(INFO_TARGETS): Use $INFO_EXT.
Make all rules generating info files use $INFO_EXT, $INFO_OPT, and -o.
* doc/misc/makefile.w32-in (INFO_EXT, INFO_OPTS): New.
(INFO_TARGETS): Use $INFO_EXT.
Make all rules generating info files use $INFO_EXT, $INFO_OPT, and -o.