Add NDK version of MediaMuxer

and add some constness here and there.

Change-Id: Ib3caa8310691e8f27aaa1afcfaec0b384513d4f1
diff --git a/media/ndk/NdkMediaFormatPriv.h b/media/ndk/NdkMediaFormatPriv.h
index f67e782..02342d9 100644
--- a/media/ndk/NdkMediaFormatPriv.h
+++ b/media/ndk/NdkMediaFormatPriv.h
@@ -34,7 +34,7 @@
 #endif
 
 AMediaFormat* AMediaFormat_fromMsg(void*);
-void AMediaFormat_getFormat(AMediaFormat* mData, void* dest);
+void AMediaFormat_getFormat(const AMediaFormat* mData, void* dest);
 
 #ifdef __cplusplus
 } // extern "C"