Remove unused header file

Nothing uses the definition it contains (I've tested spice-gtk and
spice)

common/Makefile.am

@@ -40,7 +40,6 @@ libspice_common_la_SOURCES =		\
 	mem.c				\
 	mem.h				\
 	messages.h			\
-	mutex.h				\
 	pixman_utils.c			\
 	pixman_utils.h			\
 	quic.c				\

common/canvas_base.c

@@ -42,7 +42,6 @@
 #include "rop3.h"
 #include "mem.h"
 #include "macros.h"
-#include "mutex.h"
 
 #define ROUND(_x) ((int)floor((_x) + 0.5))
 

common/mutex.h

@@ -1,42 +0,0 @@
-/* -*- Mode: C; c-basic-offset: 4; indent-tabs-mode: nil -*- */
-/*
-   Copyright (C) 2009 Red Hat, Inc.
-
-   This library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   This library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with this library; if not, see <http://www.gnu.org/licenses/>.
-*/
-
-#ifndef _H_MUTEX
-#define _H_MUTEX
-
-#include <spice/macros.h>
-
-SPICE_BEGIN_DECLS
-
-#ifdef _WIN32
-#include <windows.h>
-typedef CRITICAL_SECTION mutex_t;
-#define MUTEX_INIT(mutex) InitializeCriticalSection(&mutex)
-#define MUTEX_LOCK(mutex) EnterCriticalSection(&mutex)
-#define MUTEX_UNLOCK(mutex) LeaveCriticalSection(&mutex)
-#else
-#include <pthread.h>
-typedef pthread_mutex_t mutex_t;
-#define MUTEX_INIT(mutex) pthread_mutex_init(&mutex, NULL);
-#define MUTEX_LOCK(mutex) pthread_mutex_lock(&mutex)
-#define MUTEX_UNLOCK(mutex) pthread_mutex_unlock(&mutex)
-#endif
-
-SPICE_END_DECLS
-
-#endif // _H_MUTEX