Use bool instead of bool_t

bool is one of the built in, standard types in C++, there's no need
for a typedef for it.

codec/decoder/core/src/pic_queue.cpp

@@ -149,4 +149,4 @@ PPicture PrefetchPic (PPicBuff pPicBuf) {
   return pPic;
 }
 
-} // namespace WelsDec
+} // namespace WelsDec