First set of changes for mips16:

First set of changes for mips16:
	* config/mips/tm-mips.h (MIPS16_BIG_BREAKPOINT,
	MIPS16_LITTLE_BREAKPOINT, BREAKPOINT_FROM_PC): Define.
	(ABOUT_TO_RETURN): Call new function mips_about_to_return.
	(mips_breakpoint_from_pc, mips_about_to_return): Declare.
	* mem-break.c (memory_breakpoint_from_pc): New function.
	(memory_insert_breakpoint, memory_remove_breakpoint): Use
	memory_breakpoint_from_pc to determine breakpoint contents and size.
	* target.h (memory_breakpoint_from_pc): Declare.
	* monitor.c (monitor_insert_breakpoint): Use memory_breakpoint_from_pc
	to determine size of breakpoint instruction.
	* mips-tdep.c (mips32_decode_reg_save, mips16_decode_reg_save):
	New helper functions for mips_find_saved_regs.
	(mips_find_saved_regs): Recognize mips16 prologues.
	(mips_addr_bits_remove): Strip off upper 32 bits of address
	when target CPU is 32 bits but CORE_ADDR is 64 bits.
	(mips_step_skips_delay): No branch delay slot on mips16.
	(gdb_print_insn_mips): Disassemble mips16 code.
	(mips_breakpoint_from_pc, mips_about_to_return): New functions.