[MLton] -default-ann syntax

[Stephen Weeks]

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?