[MLton] Patch to make ML-Yacc output line directives

[Matthew Fluet]

On Tue, 18 Dec 2007, Vesa Karvonen wrote:
> While browsing code with the def-use mode, it is somewhat annoying to
> end up in some generated file, such as a file generated by mlyacc.

I've also found it annoying when trying to track down type-errors in 
semantic actions from mlyacc grammers.  The patch has my vote.  (Although 
I haven't tried it.)