* gdbarch.sh (struct regcache): Add opaque declaration.

* gdbarch.sh (struct regcache): Add opaque declaration.
(EXTRACT_RETURN_VALUE): New architecture method.
(EXTRACT_STRUCT_VALUE_ADDRESS): Ditto.
* gdbarch.h, gdbarch.c: Regenerate.
* arch-utils.c (legacy_extract_return_value): New function.
* arch-utils.h (legacy_extract_return_value): Declare.
* values.c (value_being_returned): Re-enable code handling
EXTRACT_STRUCT_VALUE_ADDRESS.  Move
deprecated_grub_regcache_for_registers call to block handling
DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS.
(EXTRACT_RETURN_VALUE): Do not define.