avutil/log: use thread wrappers for the locking functionality

w32threads and os2threads both support static mutex initialization now,
so don't limit it to pthreads only.
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavutil/log.c

@@ -39,11 +39,9 @@
 #include "common.h"
 #include "internal.h"
 #include "log.h"
+#include "thread.h"
 
-#if HAVE_PTHREADS
-#include <pthread.h>
-static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
-#endif
+static AVMutex mutex = AV_MUTEX_INITIALIZER;
 
 #define LINE_SZ 1024
 
@@ -317,9 +315,7 @@ void av_log_default_callback(void* ptr, int level, const char* fmt, va_list vl)
 
     if (level > av_log_level)
         return;
-#if HAVE_PTHREADS
-    pthread_mutex_lock(&mutex);
-#endif
+    ff_mutex_lock(&mutex);
 
     format_line(ptr, level, fmt, vl, part, &print_prefix, type);
     snprintf(line, sizeof(line), "%s%s%s%s", part[0].str, part[1].str, part[2].str, part[3].str);
@@ -356,9 +352,7 @@ void av_log_default_callback(void* ptr, int level, const char* fmt, va_list vl)
 #endif
 end:
     av_bprint_finalize(part+3, NULL);
-#if HAVE_PTHREADS
-    pthread_mutex_unlock(&mutex);
-#endif
+    ff_mutex_unlock(&mutex);
 }
 
 static void (*av_log_callback)(void*, int, const char*, va_list) =