tinydtls: add android logging support

tinydtls: add android logging support

This patch forwards the logging messages form tinydtls to the normal
android logging system instead of writing them to stdout and stderr.
This is activated in non release builds.

Change-Id: I56cf6752267dc512bf8252dfaaf957d0f87e5bf1
Signed-off-by: Hauke Mehrtens <hauke.mehrtens@lantiq.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2925
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sachin Agrawal <sachin.agrawal@intel.com>