* configure.in: Rewrite to use autoconf.

	* configure.in: Rewrite to use autoconf.
	* configure.host: New file.
	* configure.tgt: New file.
	* aclocal.m4: New file.
	* configure: New file, built by autoconf.
	* acconfig.h: New file.
	* config.h.in: New file, built by autoheader.
	* sysdep.h: New file.
	* ld.h: Incorporate old contents of config.h.
	* config.h: Remove.
	* Makefile.in: Various changes for new configure script.  Also:
	(CC_FOR_BUILD): Remove.
	(ldmain.o): Don't bother to ensure that EMUL is non-empty.
	(dep.sed): Use @SRCDIR@, not @srcdir@.
	* dep-in.sed: Use @SRCDIR@, not @srcdir@.
	* genscripts.sh: Create ldscripts if it does not exist.
	* ldemul.c, lexsup.c, mpw-emipsidt.c: Don't include "config.h".
	* mpw-esh.c, emultemp/*.em: Likewise.
	* ldmain.c: Likewise.  Include <ctype.h>.  Don't try to set
	HAVE_SBRK here.
	* config/*.mt, config/*.mh: Remove.