Windows platform change only: compile without U_CFG_MUTEX_DEBUG.
Commit #6764d2b60 brought in changes/fixes for U_CFG_MUTEX_DEBUG however, in doing so, the Windows platform ended up requiring U_CFG_MUTEX_DEBUG to be defined in order to compile.  This commit removes that requirement once more.
#include "u_port_os.h"
#include "u_port_private.h"
+
+#ifdef U_CFG_MUTEX_DEBUG
/** Grab the handle of the mutex watchdog task; this is so
* that, on Windows, when we simulate a critical section, we can
* leave it running to catch situations where we might end up
* sitting in a critical section for _far_ longer than we should..
*/
extern uPortTaskHandle_t gMutexDebugWatchdogTaskHandle;
-
+#else
+uPortTaskHandle_t gMutexDebugWatchdogTaskHandle = NULL;
+#endif
/* ----------------------------------------------------------------
* COMPILE-TIME MACROS
* -------------------------------------------------------------- */
