* defs.h: If TARGET_BYTE_ORDER_SELECTABLE is defined by tm.h,

	* defs.h: If TARGET_BYTE_ORDER_SELECTABLE is defined by tm.h,
	define TARGET_BYTE_ORDER as target_byte_order, and declare
	target_byte_order as an extern int, and define BITS_BIG_ENDIAN as
	a test of TARGET_BYTE_ORDER.
	* top.c: Several additions if TARGET_BYTE_ORDER_SELECTABLE is
	defined:
	(endianlist, target_byte_order): New variables.
	(set_endian, set_endian_big, set_endian_little): New functions.
	(show_endian): New function.
	(init_cmd_lists): Initialize endianlist.
	(init_main): Add commands ``set endian big'', ``set endian
	little'', and ``show endian''.
	* a29k-pinsn.c: Rewrite uses of TARGET_BYTE_ORDER and
	BITS_BIG_ENDIAN to switch at run time rather than at compile time.
	* coffread.c, dwarfread.c, findvar.c, mips-tdep.c: Likewise.
	* remote-os9k.c, stabsread.c, valarith.c, valprint.c: Likewise.
	* values.c: Likewise.
	* mips-tdep.c: Rewrite uses of GDB_TARGET_IS_MIPS64 to switch at
	run time rather than at compile time.