LP#1485374: add way for C code to make TZ-aware subrequests

LP#1485374: add way for C code to make TZ-aware subrequests

This patch adds a helper routine to allow C
methods to make subrequests that pass the client
time zone along. This helper is in turn used during
authentication to ensure that the user object
that is returned has timestamps that are in the
time zone of the client that makes the original
authentication request.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Mike Rylander <mrylander@gmail.com>
Conflicts:
	Open-ILS/src/c-apps/oils_auth.c