use c++-friendly initializers for pthread initializer definitions

these will also avoid obnoxious warnings with gcc -Wbraces.

include/pthread.h

@@ -53,9 +53,9 @@ extern "C" {
 #define PTHREAD_PROCESS_SHARED 1
 
 
-#define PTHREAD_MUTEX_INITIALIZER {0}
-#define PTHREAD_RWLOCK_INITIALIZER {0}
-#define PTHREAD_COND_INITIALIZER {0}
+#define PTHREAD_MUTEX_INITIALIZER {{{0}}}
+#define PTHREAD_RWLOCK_INITIALIZER {{{0}}}
+#define PTHREAD_COND_INITIALIZER {{{0}}}
 #define PTHREAD_ONCE_INIT 0