Code refactoring of toggle-ref support

Code refactoring of toggle-ref support

* alloc.c (GC_stopped_mark): Move GC_process_togglerefs() call from
GC_stop_world; do not call it if GC_NO_FINALIZATION or
GC_TOGGLE_REFS_NOT_NEEDED.
* darwin_stop_world.c (GC_stop_world): Remove GC_process_togglerefs()
call.
* pthread_stop_world.c (GC_stop_world): Likewise.
* doc/README.macros (GC_TOGGLE_REFS_NOT_NEEDED): Document.
* finalize.c (GCToggleRef, GC_process_togglerefs, push_and_mark_object,
GC_clear_togglerefs, GC_toggleref_add): Replace GC_PTR with void*.
* include/gc.h (GC_toggleref_add): Likewise.
* finalize.c (GCToggleRef, GC_toggleref_callback, GC_toggleref_arr,
GC_toggleref_array_size, GC_toggleref_array_capacity,
GC_process_togglerefs, push_and_mark_object, GC_mark_togglerefs,
GC_clear_togglerefs, GC_set_toggleref_func, ensure_toggleref_capacity,
GC_toggleref_add): Do not defined if GC_TOGGLE_REFS_NOT_NEEDED.
* finalize.c (GCToggleRef): Add comment.
* finalize.c (GC_toggleref_array): Rename to GC_toggleref_arr.
* finalize.c (GC_toggleref_callback, GC_toggleref_array,
GC_toggleref_array_size, GC_toggleref_array_capacity): Make it STATIC
(instead "static").
* finalize.c (GC_process_togglerefs): Decorate with GC_INNER; remove
"toggle_ref_counts", "res" local variables; rename "w" local variable
to "new_size"; add assertion on lock state; use GC_TOGGLE_REF_* enum
element in switch statement; use BZERO to clear moved elements of
GC_toggleref_arr.
* finalize.c (GC_normal_finalize_mark_proc): Declare (before use).
* finalize.c (push_and_mark_object): Replace PUSH_OBJ with
GC_normal_finalize_mark_proc call.
* finalize.c (GC_mark_togglerefs, GC_clear_togglerefs): Remove
"object" local variable.
* finalize.c (GC_toggleref_register_callback): Rename to
GC_set_toggleref_func; change argument to GC_toggleref_func (which
returns GC_ToggleRefStatus instead of int).
* finalize.c (GC_toggleref_register_callback, GC_toggleref_add):
Decorate with GC_API and GC_CALL.
* include/gc.h (GC_toggleref_register_callback): Likewise.
* finalize.c (GC_set_toggleref_func): Acquire allocation lock.
* finalize.c (GC_get_toggleref_func): New API function.
* finalize.c (ensure_toggleref_capacity): Rename "capacity" argument
to "capacity_inc"; add assertion on argument value; rename "tmp" local
variable to "new_array"; remove unused "old_capacity" variable; replace
memcpy() with BCOPY() call.
* finalize.c (GC_toggleref_add): Rename "strong_ref" argument to
"is_strong_ref".
* finalize.c (GC_finalize): Do not call GC_clear_togglerefs and
GC_mark_togglerefs if GC_TOGGLE_REFS_NOT_NEEDED.
* include/gc.h (GC_ToggleRefStatus, GC_toggleref_func): New type.
* include/gc.h (GC_toggleref_register_callback): Add comment
(including about locking).
* include/gc.h (GC_get_toggleref_func): New API function declaration.
* include/gc.h (GC_toggleref_add): Decorate with GC_CALL; add comment;
add GC_ATTR_NONNULL attribute.
* include/private/gc_priv.h (GC_process_togglerefs): Do not declare if
GC_TOGGLE_REFS_NOT_NEEDED; decorate with GC_INNER.