message: use utils::Mutex instead of std::mutex for Allocators locking policy
  on Android it's about 2x faster and uses much less instructions, which
  is better for i-cache pressure.
diff: #include <utils/compiler.h>
  #include <utils/memalign.h>
  +#include <utils/Mutex.h>
  namespace utils {
  @@ -468,7 +469,7 @@ private:
  }
  };
  -using Mutex = std::mutex;
  +using Mutex = utils::Mutex;
  } // namespace LockingPolicy
  