[MLton] Emacs mode for editing ML Basis files

[Matthew Fluet]

> > I left it as doc/emacs.  Since directories and files are movable
> > with history, I'm less concerned about reorganizing in the face of
> > future developments.
> 
> True.  I will point out that ide/emacs has the virtue of making sense
> on its own.

Fair enough.  

As long as we're organizing things conceptually, how about:

doc/emacs  --->  ide/emacs
doc/mlton.spec  --->  packages/rpm/mlton.spec
debian  --->  packages/debian
freebsd  --->  packages/freebsd
doc/cmcat  --->  utils/cmcat
doc/cm2mlb  --->  utils/cm2mlb