[MLton] cvs commit: world no longer contains a preprocessed basis library

[Stephen Weeks]

> I  guess  that  what  I am asking for is another directive for the .mlb files
> which means to include any of this stuff if it is `used', where `used' should
> be  interpreted  as it is for the basis.  I.e., more stuff is considered dead
> code.

I will add some kind of directive like this, at the very least so we
can move the basis libary stuff as much as possible into mlb files.
However, the dead-code hack used for the basis library is unsafe in
general and almost certainly too aggressive for normal code.  It works
on the granularity of declarations.  I am thinking that the default
granularity for mlb files will be at the level of files.