s390-protos.h (s390_hard_regno_rename_ok): Add prototype.

	* config/s390/s390-protos.h (s390_hard_regno_rename_ok): Add prototype.
	* config/s390/s390.c (s390_hard_regno_rename_ok): New function.
	(s390_can_eliminate): Handle BASE_REGNUM elimination.
	(s390_initial_elimination_offset): Likewise.
	(s390_conditional_register_usage): BASE_REGNUM is no longer a fixed
	register on TARGET_ZARCH targets.
	* config/s390/s390.h (HARD_REGNO_RENAME_OK): Define
	(INITIAL_FRAME_POINTER_OFFSET): Remove.
	(REG_ALLOC_ORDER): Move BASE_REGNUM lower.
	(ELIMINABLE_REGS): Add BASE_REGNUM elimination rule.

From-SVN: r105611