[IOT-2012] Windows: rename ocpmapi.lib

[IOT-2012] Windows: rename ocpmapi.lib

Windows exports ocpmapi APIs from octbstack.dll. IoTivity sample apps
and apps outside IoTivity should link with import library octbstack.lib
rather than the static library ocpmapi.lib. To expose possible
incorrect linking with ocpmapi.lib, rename it to ocpmapi_internal.lib
on Windows.

Change-Id: Ieec1abc65651c3b69674acc7419c87f8ef50d3a4
Signed-off-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/18777
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>