[MLton] x86_64 port status

[Matthew Fluet]

> Another warning I see a number of times on Solaris is the following.
>
> basis/System/Date.c:40: warning: no previous prototype for `Date_localOffset'
> basis/System/Date.c:40: warning: declaration of `Date_localOffset' shadows a global declaration
> basis-ffi.h:7: warning: shadowed declaration is here

I don't understand these errors; they seem to be self-contradictory. 
Could there be other errors before these that would lead to this?

The purpose of basis-ffi.h is to provide prototypes for all of the 
_import-ed functions in used in the Basis Library.  So, I expect 
Date_localOffset to appear there, and it should provide the prototype.