libmediaplayerservice: fix warnings, make warnings errors, use clang

Change-Id: I1b2f6b65c5abbc366068a60b8909104f31b94228
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerCCDecoder.cpp b/media/libmediaplayerservice/nuplayer/NuPlayerCCDecoder.cpp
index cf3e8ad..ac3c6b6 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerCCDecoder.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerCCDecoder.cpp
@@ -51,6 +51,7 @@
     return cc->mData1 < 0x10 && cc->mData2 < 0x10;
 }
 
+static void dumpBytePair(const sp<ABuffer> &ccBuf) __attribute__ ((unused));
 static void dumpBytePair(const sp<ABuffer> &ccBuf) {
     size_t offset = 0;
     AString out;