AudioFileMp3 - handle clipping better

Fixed bug - when a sample clipped it was causing an overflow, making
random noise where clipping happened. Now it clips properly.

TODO

@@ -55,7 +55,7 @@ Andrew Kelley's todo:
 * when you press down or up while browsing the resource browser, it should
   play the sample
 * select the output file format based on what you selected in file->save as
-* segfault when you export an mp3 and press cancel
+* ability to read mp3 samples
 
 
 - automation recording:

src/core/audio/audio_file_mp3.cpp

@@ -276,7 +276,7 @@ bool AudioFileMp3::startEncoding( void )
 
 
 short int AudioFileMp3::rescale(float sample) {
-    return (sample / 1) * std::numeric_limits<short int>::max();
+    return (qMin<float>(sample, 1) / 1) * std::numeric_limits<short int>::max();
 }
 
 // encode data and write to file