IOT-1073 Enable AutoConf header file CPPDEFINES

IOT-1073 Enable AutoConf header file CPPDEFINES

This change enables inclusion of header files based on the presence of
the headers themselves.

Change-Id: I742a02911b20f77fb6f05c75611784f01ad86b3b
Signed-off-by: David Antler <david.a.antler@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/7861
Reviewed-by: Dave Thaler <dthaler@microsoft.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>