WAV file extension is appended

[maxim-zhao]

The docs say:

\<name> IS NOT checked for or appended with a legal wav file extension.

This used to be true, but the current code does this:

title.append(WavFile::extension());

Can you make it do one or the other? Ideally, it might add the extension only if the passed filename doesn't already have it.

[drfiemost]

Fixed with the above commit, now it adds the extension only if not already provided.

[maxim-zhao]

Thanks!