[MLton] mlb support

[Henry Cejtin]

Re inode changing and the like, why not just check them on startup each time.
I.e., stash away in the saved world, the device, inode and ctime.  (The ctime
changes  when  you do any thing to the file except rename it.  All ops change
the ctime to the current time and there is no way to  set  the  ctime  back.)
This  way  if files are changed in any way, the stamp would change.  In cases
where a saved basis file turned out to be invalid on a run (because of  these
having  changed)  you  would  issue a warning to stderr saying that the cache
should be re-built, and, for that run, read them in again.

Re short names, I agree that it isn't a big deal, but I find it  annoying  to
have  to read stuff just to make sure that it is what it almost certainly is.
Any way, clearly not really important either way.