[MLton] a few remaining Solaris bugs with the new runtime

[Stephen Weeks]

I've successfully cross-compiled MLton to run on Solaris with the new
runtime.  The resulting MLton compiles all the regressions, and there
is only one regression failure: echo.sml, which reports

  unhandled exception: Error

instead of

  server processed 1900 bytes

The only other failures I see are in testing the stuff in
doc/examples.  ffi/export fails with

  Illegal Instruction (core dumped)

and profile/tak, when compiled with -profile time, segfaults.

If anyone's encountered similar errors with the new runtime, please
speak up.  Else I'll start plowing through the bugs.