Backwards compatibility: \compressMusic, \scaleDurations, WHY WHY WHY

[Steve Dunlop]

<rant>

You have absolutely no idea how much chaos things like this cause for
people who are using Lilypond for major projects.  You have absolutely
no idea how much of a problem this sort of thing is for archives like
Mutopia.  You have no idea how the lack of input grammar stability
undermines efforts for wider adoption of Lilypond for projects like
Gutenburg and Wikipedia.

If you want to change the syntax, fine, add the new, update the
documentation, but for heaven's sake leave the old syntax alone so that
existing files will still compile.

</rant>