gdb: move displaced stepping types to displaced-stepping.{h,c}

gdb: move displaced stepping types to displaced-stepping.{h,c}

Move displaced-stepping related stuff unchanged to displaced-stepping.h
and displaced-stepping.c.  This helps make the following patch a bit
smaller and easier to read.

gdb/ChangeLog:

	* Makefile.in (COMMON_SFILES): Add displaced-stepping.c.
	* aarch64-tdep.h: Include displaced-stepping.h.
	* displaced-stepping.h (struct displaced_step_copy_insn_closure):
	Move here.
	(displaced_step_copy_insn_closure_up): Move here.
	(struct buf_displaced_step_copy_insn_closure): Move here.
	(struct displaced_step_inferior_state): Move here.
	(debug_displaced): Move here.
	(displaced_debug_printf_1): Move here.
	(displaced_debug_printf): Move here.
	* displaced-stepping.c: New file.
	* gdbarch.sh: Include displaced-stepping.h in gdbarch.h.
	* gdbarch.h: Re-generate.
	* inferior.h: Include displaced-stepping.h.
	* infrun.h (debug_displaced): Move to displaced-stepping.h.
	(displaced_debug_printf_1): Likewise.
	(displaced_debug_printf): Likewise.
	(struct displaced_step_copy_insn_closure): Likewise.
	(displaced_step_copy_insn_closure_up): Likewise.
	(struct buf_displaced_step_copy_insn_closure): Likewise.
	(struct displaced_step_inferior_state): Likewise.
	* infrun.c (show_debug_displaced): Move to displaced-stepping.c.
	(displaced_debug_printf_1): Likewise.
	(displaced_step_copy_insn_closure::~displaced_step_copy_insn_closure):
	Likewise.
	(_initialize_infrun): Don't register "set/show debug displaced".

Change-Id: I29935f5959b80425370630a45148fc06cd4227ca