lib/replace: split out GSSAPI from lib/replace/system/kerberos.h into lib/replace...

lib/replace: split out GSSAPI from lib/replace/system/kerberos.h into lib/replace/system/gssapi.h

With waf build include directories are defined by dependencies specified to subsystems.
Without proper dependency <gssapi/gssapi.h> cannot be found for embedded Heimdal builds
when there are no system-wide gssapi/gssapi.h available.

Split out GSSAPI header includes in a separate replacement header and use that explicitly
where needed.

Autobuild-User: Alexander Bokovoy <ab@samba.org>
Autobuild-Date: Wed Apr 25 00:18:33 CEST 2012 on sn-devel-104