* acinclude.m4 (GNUPG_CHECK_MLOCK): Check also for EAGAIN which is a
legitimate return code and does not indicate a broken mlock().
* src/secmem.c (lock_pool_pages): Test ERR instead of ERRNO which
could have been overwritten by cap_from+text et al.

On FreeBSD, if there are not enough free pages, mlock() can return
EAGAIN, as documented in mlock(2). That doesn't mean that mlock is
broken. I suspect this same issue also exists on the other BSD's.