[Win32] Rename 'interface' to satisfy Windows.h

[Win32] Rename 'interface' to satisfy Windows.h

Definitions including the name 'interface' were conflicting
with Windows.h. Some were changed to ifindex, and others
were changed to iface, depending on the context.

Change-Id: I7e7ded6587736c09307fa41bc6d90202d6ab0554
Signed-off-by: Henry Beberman <henry.beberman@intel.com>
Signed-off-by: Daniel Ferguson <daniel.j.ferguson@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/5561
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: David Antler <david.a.antler@intel.com>