space profiling

[Henry Cejtin]

In  my  mail,  the  reason for the `save flags some where' and `restore flags
from some where' was the idea that the entire  rest  of  the  code  generator
could  be  completely unaware that any thing was going on.  If this is no big
deal to the code generator, then it looks like the 2 parallel arrays  is  the
way to go.

As to the 64 bit integer support, for now just using IntInf's should be fine.
It isn't like mlprof does  much.   As  to  the  code  in  the  program  being
profiled, I would still probably vote (weakly) for doing this in C.  With the
global nature of MLton, any ML code could cause changes in other things.