IOT-1583: Disabling harmless /W4 warnings.

IOT-1583: Disabling harmless /W4 warnings.

In preparation for libcoap /W4 fixes we're disabling warnings,
which do not cause any potential issues.

Change-Id: I136b34f2d5824efcc052b2c7f3a0b8315c8f3f23
Signed-off-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17639
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Alex Kelley <alexke@microsoft.com>
Reviewed-by: Mike Fenelon <mike.fenelon@microsoft.com>