rtl.h (traverse_md_constants): Declare.

	* rtl.h (traverse_md_constants): Declare.
	(struct md_constant): Define.
	* Makefile.in (HOST_RTL): Add hashtab.o .
	(OBJS): Add hashtab.o .
	(hashtab.o): New rule.
	(rtl.o): Depends on HASHTAB_H.
	* rtl.c (hashtab.h): #include.
	(md_constants): New static variable.
	(def_hash, def_name_eq_p, read_constants): New static functions.
	(traverse_md_constants): New function.
	(read_name): Do constant expansion.
	(read_rtx): Recognize define_constants.
	* gencodes.c (print_md_constant): New function.
	(main): Emit #defines for all constant definitions encountered.
	* md.texi (Constant Definitions): New node.
	* gensupport.c (xcalloc): New function.

From-SVN: r37635