various changes from sm4 and sm-ssc (svn); see updated changelog for the full information

src/RageFileManager_ReadAhead.h

@@ -8,9 +8,13 @@ namespace RageFileManagerReadAhead
 	void Init();
 	void Shutdown();
 
-	/* Nonblockingly read bytes from a file. */
+	// Nonblockingly read ahead iBytes in pFile, starting at the current file position.
 	void ReadAhead( RageFileBasic *pFile, int iBytes );
 
+	/* Discard iBytes of kernel cache, starting at the current file position plus
+	 * iRelativePosition (which may be negative). */
+	void DiscardCache( RageFileBasic *pFile, int iRelativePosition, int iBytes );
+
 	void CacheHintStreaming( RageFileBasic *pFile );
 };