commit 618b18c7 removed the previous
detection and hardening since it was incorrect. commit
72141795 already handled all that
remained for hardening the static-linked case. in the dynamic-linked
case, have the dynamic linker check whether malloc was replaced and
make that information available.

with these changes, the properties documented in commit
c9f415d7 are restored: if calloc is
not provided, it will behave as malloc+memset, and any of the
memalign-family functions not provided will fail with ENOMEM.