PLEASE: no horrible HEAP_SUFFIX junk

[Stephen Weeks]

> Please,  get rid of that horrible HEAP_SUFFIX code in the mlton shell script.
> Note, it isn't used at all, thank god  (the  shell  variable  HEAP_SUFFIX  is
> defined  but  not  used)  and  it is incredibly ugly and stupid.  Just delete
> everything from the definition of HEAP_SUFFIX through the commented out `fi'.
> It  is  so  much  nicer  that  way.  If some goofy person wants to try to use
> SML/NJ to compile MLton on a non-Linux box, they are going to  need  to  know
> all  kinds  of  things.   The ability to change the dumped heap suffix is the
> least of their worries.  It isn't worth uglifying  the  MLton  script,  which
> doesn't even use SML/NJ, just in this odd case.

OKOK.  It was in there because Dimock had requested it at some point.