Misc cleanup for doc/*/Makefiles.

Misc cleanup for doc/*/Makefiles.

* doc/misc/Makefile.in (SHELL): Set it.
(info): Move the mkdir dependency to the individual info files.
(mostlyclean): Tidy up.
(clean): Only delete the specific dvi and pdf files.
(maintainer-clean): Be more restrictive in what we delete.

* doc/lispref/Makefile.in: Rearrange to more closely resemble
doc/emacs/Makefile.
(INSTALL_INFO): Remove unused variable.
(mostlyclean, infoclean, dist): New rules.
(clean): Delete dvi and pdf files.
(maintainer-clean): Remove elisp.oaux, use infoclean.

* doc/lispintro/Makefile.in (SHELL): Use /bin/sh, like every other Makefile.in.
(INFO_SOURCES, INFO_TARGETS, DVI_TARGETS): Remove variables.
($(infodir), html, pdf, infoclean, dist): New rules.
(${infodir}/eintr): Ensure $infodir exists.  Use $@.
(emacs-lisp-intro.dvi, emacs-lisp-intro.pdf, emacs-lisp-intro.html): Use $^.
(.PHONY): Declare clean rules.
(mostlyclean): Delete more temp files.
(clean): Delete specific dvi, pdf and html files.
(maintainer-clean): Use infoclean.
(.NOEXPORT): Remove, unused by any other Makefile.in.

* doc/emacs/Makefile.in (EMACS_XTRA): Add the main source file.
(emacs-xtra.dvi, emacs-xtra.pdf): Remove explicit emacs-xtra.texi.
(mostlyclean): No core files, reorder other files.
(clean): Delete specific dvi and pdf files.
(infoclean, dist): New rules.
(maintainer-clean): Use infoclean.