Windows API DLL (#882)

* VS Solution files and minor fixes.

* Move Tasklet into platform include file

* Refactor data path APIs into openthread-ip6.h

src/cli/cli.cpp

@@ -2033,6 +2033,10 @@ void Interpreter::ProcessState(int argc, char *argv[])
     {
         switch (otGetDeviceRole(mInstance))
         {
+        case kDeviceRoleOffline:
+            sServer->OutputFormat("offline\r\n");
+            break;
+
         case kDeviceRoleDisabled:
             sServer->OutputFormat("disabled\r\n");
             break;