[MLton] -default-ann syntax

[Matthew Fluet]

> I was wondering if it would be worth allowing/requiring a different
> syntax for annotations appearing on the command line in -default-ann,
> due to the fact that the shell already treats spaces as a word
> separator.  I wonder if
>
> 	-default-ann allowImport=true
>
> might be easier to use than
>
> 	-default-ann 'allowImport true'
>
> This is especially true when one wants to use shell variables to build
> parts of the command line.  See the eval hackery that I had to do in
> bin/regression to make it work.
>
> Thoughts?

I'd prefer to keep the syntax the same in both places.  But, I don't
object to using "=" in both places.