Add support for needed functionality to mbedTLS

Add support for needed functionality to mbedTLS

Support for directoryName-based subject alternative name
Creating certificates containing this extension
Specifying a particular EKU to check for in TLS negotiation instead
of standard client/server authentication EKUs

This work will be offered upstream to the mbedTLS maintainers; if
they accept it, this will later be reverted when IoTivity ingests
a newer version of mbedTLS.

Change-Id: I4f81d75b767683327564e27758d1aa1bc02613de
Signed-off-by: Kevin Kane <kkane@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/15733
Reviewed-by: Alex Kelley <alexke@microsoft.com>
Reviewed-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Oleksii Beketov <ol.beketov@samsung.com>
Reviewed-by: dongik Lee <dongik.lee@samsung.com>
Reviewed-by: Greg Zaverucha <gregz@microsoft.com>