use URL prefixes to also check for authentication of custom URLs

For load balancing "/urlprefix outputs the list of URL prefixes that
are handled in the ABAP part of the SAP Web AS". This list also
contains URLs of custom programs (z-programs). Using this information
the module will now also check authentication of these URLs. See http://help.sap.com/saphelp_nw04/helpdata/en/a8/a8463c53a0ff02e10000000a114084/content.htm
Note, that /urlprefix may or may not be public accessible.