Return 1 from SetPosition(n) on success, 0 on seek past EOF, not

"the position seeked to".  This fixes a special case: SetPosition(n)
returning 0 was EOF except when SetPosition(0).  The returned value
on success was always n, anyway; we never seek to a different position
and return success.

stepmania/src/RageSoundReader_Vorbisfile.cpp

@@ -157,7 +157,7 @@ int RageSoundReader_Vorbisfile::SetPosition( int iFrame )
 	}
 	read_offset = (int) ov_pcm_tell(vf);
 
-	return iFrame;
+	return 1;
 }
 
 int RageSoundReader_Vorbisfile::Read( char *buf, int iFrames )