Move SoundReader::OpenFile to SoundReader_FileReader.

Add file format fallbacks, to handle misnamed files.

stepmania/src/RageSoundReader_FileReader.h

@@ -6,7 +6,18 @@
 
 class SoundReader_FileReader: public SoundReader {
 public:
-	virtual bool Open(CString filename) = 0;
+	/* Return OPEN_OK if the file is open and ready to go.  Return OPEN_NO_MATCH
+	 * if the file appears to be of a different type.  Return OPEN_MATCH_BUT_FAIL if
+	 * the file appears to be the correct type, but there was an error initializing
+	 * the file.
+	 *
+	 * If the file can not be opened at all, or contains no data, return OPEN_MATCH_BUT_FAIL. */
+	enum OpenResult { OPEN_OK, OPEN_NO_MATCH, OPEN_MATCH_BUT_FAIL };
+	virtual OpenResult Open(CString filename) = 0;
+
+	static SoundReader *OpenFile( CString filename, CString &error );
+private:
+	static SoundReader_FileReader *TryOpenFile( CString filename, CString &error, CString format );
 };
 
 #endif