* gdbarch.sh (make_corefile_notes): New architecture callback.

	* gdbarch.sh (make_corefile_notes): New architecture callback.
	* gdbarch.c: Regenerate.
	* gdbarch.h: Likewise.

	* gcore.c (write_gcore_file): Try gdbarch_make_corefile_notes
	before target_make_corefile_notes.  If NULL is returned, the
	target does not support core file generation.

	* linux-nat.c: Include "linux-tdep.h".
	(find_signalled_thread, find_stop_signal): Remove.
	(linux_nat_do_thread_registers): Likewise.
	(struct linux_nat_corefile_thread_data): Likewise.
	(linux_nat_corefile_thread_callback): Likewise.
	(iterate_over_spus): Likewise.
	(struct linux_spu_corefile_data): Likewise.
	(linux_spu_corefile_callback): Likewise.
	(linux_spu_make_corefile_notes): Likewise.
	(linux_nat_collect_thread_registers): New function.
	(linux_nat_make_corefile_notes): Replace contents by call to
	linux_make_corefile_notes passing linux_nat_collect_thread_registers
	as native-only callback.

	* linux-tdep.h: Include "bfd.h".
	(struct regcache): Add forward declaration.
	(linux_collect_thread_registers_ftype): New typedef.
	(linux_make_corefile_notes): Add prototype.
	* linux-tdep.c: Include "gdbthread.h", "gdbcore.h", "regcache.h",
	"regset.h", and "elf-bfd.h".
	(find_signalled_thread, find_stop_signal): New functions.
	(linux_spu_make_corefile_notes): Likewise.
	(linux_collect_thread_registers): Likewise.
	(struct linux_corefile_thread_data): New data structure.
	(linux_corefile_thread_callback): New funcion.
	(linux_make_corefile_notes): Likewise.
	(linux_make_corefile_notes_1): Likewise.
	(linux_init_abi): Install it.