Do not print n_rescuing_pages value if incremental collections disabled

Do not print n_rescuing_pages value if incremental collections disabled

* mark.c (GC_n_rescuing_pages): Do not define if GC_DISABLE_INCREMENTAL
and not STUBBORN_ALLOC; refine comment.
* mark.c (GC_initiate_gc, GC_push_marked): Do not update
GC_n_rescuing_pages if GC_DISABLE_INCREMENTAL and not STUBBORN_ALLOC.
* mark.c [ENABLE_DISCLAIM] (GC_push_unconditionally): Likewise.
* mark.c (GC_mark_some_inner): Do call GC_COND_LOG_PRINTF for
GC_n_rescuing_pages if GC_DISABLE_INCREMENTAL and not STUBBORN_ALLOC.