Fix two more compile errros on Windows.

source/common/umutex.h

 /*
 **********************************************************************
 *   Copyright (C) 1997-2013, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 **********************************************************************
 *
 * File UMUTEX.H
 *
 * Modification History:
 *
@@ skipping 302 matching lines @@
 # define NOSERVICE
 # define NOIME
 # define NOMCX
 # ifndef NOMINMAX
 # define NOMINMAX
 # endif
 # include <windows.h>
 
 
 typedef struct UMutex {
-    UInitOnce         fInitOnce;
+    icu::UInitOnce         fInitOnce;
     CRITICAL_SECTION  fCS;
 } UMutex;
 
 /* Initializer for a static UMUTEX. Deliberately contains no value for the
  *  CRITICAL_SECTION.
  */
 #define U_MUTEX_INITIALIZER {U_INITONCE_INITIALIZER}
 
 
 
@@ skipping 40 matching lines @@
 U_INTERNAL void U_EXPORT2 umtx_lock(UMutex* mutex);
 
 /* Unlock a mutex.
  * @param mutex The given mutex to be unlocked.  Pass NULL to specify
  *              the global ICU mutex.
  */
 U_INTERNAL void U_EXPORT2 umtx_unlock (UMutex* mutex);
 
 #endif /* UMUTEX_H */
 /*eof*/