* configure: If CC and CXX are not set in the environment, set

	* configure: If CC and CXX are not set in the environment, set
	them, based on either an existing Makefile or on searching for gcc
	in PATH.  Substitute for CC and CXX in Makefile.
	* configure.in: Remove libm from target_libs.  Separate
	target_configdirs from configdirs.  If CC is not set in
	environment, try to get it from a host Makefile fragment.  Rewrite
	changes of configdirs to use skipdirs instead.  A few minor
	tweaks.  Take directories out of target_configdirs as they are
	taken out of configdirs.  Remove existing Makefile files from
	subdirectories.  Substitute for TARGET_CONFIGDIRS and
	CONFIG_ARGUMENTS in Makefile.
	* Makefile.in (TARGET_CONFIGDIRS): New variable, automatically set
	by configure.in.
	(CONFIG_ARGUMENTS): Likewise.
	(CONFIGURE_TARGET_MODULES): New variable.
	($(DO_X)): Loop over TARGET_CONFIGDIRS as well as SUBDIRS.
	($(CONFIGURE_TARGET_MODULES)): New target.
	(configure-libg++, configure-libio): New targets.
	(all-libg++): Depend upon configure-libg++.
	(all-libio): Depend upon configure-libio.
	(configure-libgloss, all-libgloss): New targets.
	(configure-libstdc++): New target.
	(all-libstdc++): Depend upon configure-libstdc++.
	(configure-librx, all-librx): New targets.
	(configure-newlib): New target.
	(all-newlib): Depend upon configure-newlib
	(configure-xiberty): New target.
	(all-xiberty): Depend upon configure-xiberty.