nice and small
     and could be inlined to avoid function calls.
<li> Cray: Variable length arrays seem to be faster than the tal-notreent.c
     scheme.  Not sure why, maybe they merely give the compiler more
     information about aliasing (or the lack thereof).  Would like to modify
     <code>TMP_ALLOC</code> to use them, or introduce a new scheme.  Memory
     blocks wanted unconditionally are easy enough, those wanted only
     sometimes are a problem.  Perhaps a special size calculation to ask for a