* blockframe.c (generic_find_dummy_frame): Change return type to

* blockframe.c (generic_find_dummy_frame): Change return type to
``struct regcache''.
(struct dummy_frame): Replace field ``registers'' with regcache, a
struct regcache object.
(generic_find_dummy_frame): Update.
(generic_push_dummy_frame): Update.  Use regcache_xfree,
regcache_xmalloc and regcache_cpy.
(generic_pop_dummy_frame): Update.  Use regcache_cpy and
regcache_xfree.
(deprecated_generic_find_dummy_frame): Update.
(generic_read_register_dummy): Update.  Use
regcache_read_as_address.
(generic_call_dummy_register_unwind): Update.  Use regcache_read.
(generic_get_saved_register): Update.  Use regcache_read.