profiling

[Matthew Fluet]

> I put up a snapshot at http://www.star-lab.com/sweeks/src.tgz.  

Got it.  I'm looking at the mlprof stuff and should have a working version
fairly quickly.  

One problem I ran into when compiling the new runtime is that EIP is not a
macro in my default include files.  This is a Mandrake 7.2 machine.
Looking through /usr/include/ucontext.h, it would seem that REG_EIP would
be the appropriate #define, but that's under an #ifdef __USE_GNU.
Anyways, I just hardwired it as 12 for right now, but it's something to be
aware of.