* linux-low.c (linux_prepare_to_access_memory): New.

	* linux-low.c (linux_prepare_to_access_memory): New.
	(linux_unprepare_to_access_memory): New.
	(linux_target_ops): Install them.
	* server.c (read_memory): Rename to ...
	(gdb_read_memory): ... this.  Use
	prepare_to_access_memory/prepare_to_access_memory.
	(write_memory): Rename to ...
	(gdb_write_memory): ... this.  Use
	prepare_to_access_memory/prepare_to_access_memory.
	(handle_search_memory_1): Adjust.
	(process_serial_event): Adjust.
	* target.h (struct target_ops): New fields
	prepare_to_access_memory and unprepare_to_access_memory.
	(prepare_to_access_memory, unprepare_to_access_memory): New.
	* linux-x86-low.c (x86_insert_point, x86_remove_point): Use
	prepare_to_access_memory/prepare_to_access_memory.
	* nto-low.c (nto_target_ops): Adjust.
	* spu-low.c (spu_target_ops): Adjust.
	* win32-low.c (win32_target_ops): Adjust.