Install David Mackenzie's patches to make ${srcdir} work.

Install David Mackenzie's patches to make ${srcdir} work.
	* Makefile.in (srcdir, VPATH): Get this value from the top-level
	Makefile.
	(xmakefile): Use ${srcdir} to find the files from which we produce
	xmakefile.  Edit the values for srcdir and VPATH into xmakefile.
	* ymakefile (srcdir, VPATH): New definitions for the Makefile
	to edit.
	(ALL_CFLAGS): Remove `-Is' and `-Im'; add `-I${srcdir}', and
	`-I.'.
	(emacs): Adjust dumping commands to deal with a separate source
	directory.
	(${etc}DOC): Pass `-d ${srcdir}' to make-docfile, to tell it where
	to find the source files.
	(prefix-args): Find the source code in ${srcdir}.