[IOT-1621] Add custom config.h file mbedtls build options

[IOT-1621] Add custom config.h file mbedtls build options

Adds a new version of the mbedtls config.h file specialized to IoTivity.
Library features that are not required by IoTivity are removed from the build.
The new file is extlibs/mbedtls/config-iotivity.h. Changes to config.h made by
ocf.patch are now made directly in config-iotivity.h. Update the scons file to
copy this to mbedtls/include/mbedtls/config.h. Update ssaladapter tests so that
they don't allow unsupported TLS versions.

TLS renegotiation was being disabled at runtime, now it is disabled at build.

To review the changes that IoTivity makes to config.h relative to the default,
diff extlibs/mbedtls/config-iotivity.h and
extlibs/mbedtlsmbedtls/include/mbedtls/config.h.

Change-Id: I9e6190e7c0e145443d5e164ccf47314a3bfcf53e
Signed-off-by: Greg Zaverucha <gregz@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/15175
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Kevin Kane <kkane@microsoft.com>
(cherry picked from commit 91cbd73ce34e72cad01b9912c471164a8abb3cb2)
Reviewed-on: https://gerrit.iotivity.org/gerrit/15707