Moved creating and destroying of Reader and Decoder plugins into the PluginManager class.

Removed deferred initialization from BMediaDecoder. 


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@21296 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/media/DecoderPlugin.h

@@ -39,7 +39,7 @@ public:
 	status_t			GetNextChunk(const void **chunkBuffer, size_t *chunkSize,
 									 media_header *mediaHeader);
 
-	void				Setup(ChunkProvider *provider);
+	void				SetChunkProvider(ChunkProvider *provider);
 private:
 	ChunkProvider *		fChunkProvider;
 };