Log Message:
Solarish pthreads expect mutex datastructures to be properly zeroed
out, unlike the Linux implementation, which upstream mainly
targets. This leads to "tdb_open_ex: tdb_mutex_init failed for
/var/samba/lock/gencache.tdb: Device busy" errors, described in
<https://illumos.topicbox.com/groups/developer/T28dcabf2f69cac04>.

Illumos kernel code attempted to mitigate the problem as of
<https://www.illumos.org/issues/9959>, but the changes have yet to
show up in releases.

The patches originate from
<https://github.com/oposs/pkg.oetiker.ch-build/blob/master/build/samba4/patches/pthread_mutex_init>,
modified appropriately.

Tested on omniosce r151030.