cpphash.h: Move struct reflist, struct definition, and the DEFINITION typedef to...

cpphash.h: Move struct reflist, struct definition, and the DEFINITION typedef to cpphash.c.

	* cpphash.h: Move struct reflist, struct definition, and the
	DEFINITION typedef to cpphash.c.  Use 'struct definition *' in
	union hashval.  _cpp_free_definition takes a HASHNODE pointer.
	* cpphash.c (_cpp_free_definition): Free data pointed to by
	MCONST, XCONST, MACRO, and FMACRO nodes properly.
	(_cpp_create_definition, del_HASHNODE): Just call
	_cpp_free_definition to clear out a hashnode.
	* cpplib.c (do_pragma_poison): Likewise.

From-SVN: r33536