* configure.in: Set UNDERSCORE in Makefile based on result of

	* configure.in: Set UNDERSCORE in Makefile based on result of
	invoking config.bfd with a second argument of ``_''.
	* Makefile.in (underscore.c): Depend upon Makefile.  Don't try to
	run $(CC) and $(NM), just use $(UNDERSCORE).  Create via temporary
	file.
	(demangle.o): Remove target.
	($(NM_PROG)): Don't depend upon demangle.o, and	don't link against
	demangle.o.  It's in libiberty anyhow.
	(cplus-dem.o): Don't depend upon demangle.o.
	* binutils.texi: Mention -n and --no-strip-underscores arguments
	to c++filt.