Ensure oom_fn callback executed on out-of-memory in calloc

Ensure oom_fn callback executed on out-of-memory in calloc
(Cherry-pick commit 80f428f from 'release-7_6' branch.)

* malloc.c [REDIRECT_MALLOC] (calloc):
Call oom_fn(SIZE_MAX) (instead of returning NULL) if n*lb overflows.
* typd_mlc.c (GC_calloc_explicitly_typed): Likewise.
* typd_mlc.c (GC_calloc_explicitly_typed): If register_disappearing_link
failed due to lack of memory then call oom_fn(lb) instead of
GC_malloc(lb); update comment.