Update ICU to 54.1 step 1

source/common/cmutex.h

-/*
-**********************************************************************
-*   Copyright (C) 2013, International Business Machines
-*   Corporation and others.  All Rights Reserved.
-**********************************************************************
-*
-* File cmutex.h
-*
-*     Minimal plain C declarations for ICU mutex functions.
-*     This header provides a transition path for plain C files that 
-*     formerly included mutex.h, which is now a C++ only header.
-*
-*     This header should not be used for new code.
-*
-*     C++ files should include umutex.h, not this header.
-*
-*/
-
-#ifndef __CMUTEX_H__
-#define __CMUTEX_H__
-
-typedef struct UMutex UMutex;
-
-
-/* Lock a mutex.
- * @param mutex The given mutex to be locked.  Pass NULL to specify
- *              the global ICU mutex.  Recursive locks are an error
- *              and may cause a deadlock on some platforms.
- */
-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
-