* Makefile.in (DEMANGLER): Define and default to cplus-dem.

	* Makefile.in (DEMANGLER):  Define and default to cplus-dem.
	Allows selection of C++ demangler to be a configuration option
	until multiple demanglers are supported.
	* demangle.h:  New include file for extended demangler support.
	* breakpoint.c, gdbtypes.c, printcmd.c, stack.c, symtab.c,
	utils.c, valprint.c:  Include "demangle.h" and change all calls
	to cplus_demangle() or fputs_demangled() to use individual
	demangling options.
	* valprint.c (type_print_1):  Change options to cplus_demangle
	to print demangled function args.  Still broken, but now less so.
	* cplus-dem.c:  Include demangle.h, reorganize and update some
	comments to reflect reality.
	* cplus-dem.c (cplus_demangle, cplus_mangle_opname):  Change
	second arg from fixed integer to bit based multiple options.
	* cplus-dem.c (optable):  Reformat and replace ansi members with
	bit based options.
	* cplus-dem.c (do_type):  Fix bug with parsing missing return type.