* gdbcore.h (struct regcache): Add forward declaration.

	* gdbcore.h (struct regcache): Add forward declaration.
	(struct core_fns): Add REGCACHE argument to core_read_registers
	callback.
	* corelow.c (get_core_register_section): Add REGCACHE argument,
	use it instead of current_regcache, pass it to core_read_registers
	callback.
	(get_core_registers): Add current_regcache as parameter to
	get_core_register_section calls.

	* alpha-nat.c (fetch_osf_core_registers): Add REGCACHE argument,
	use it instead of current_regcache.
	* armnbsd-nat.c (fetch_core_registers): Likewise.
	(fetch_elfcore_registers): Likewise.
	* core-regset.c (fetch_core_registers): Likewise.
	* cris-tdep.c (fetch_core_registers): Likewise.
	* irix5-nat.c (fetch_core_registers): Likewise.
	* m68klinux-nat.c (fetch_core_registers): Likewise.
	* mips-linux-tdep.c (fetch_core_registers): Likewise.
	* win32-nat.c (fetch_elf_core_registers): Likewise.