sjlj eh fixes

[Jeffrey A Law]

  In message < 19971110191302.09599@dot.cygnus.com >you write:
  > These patches fix the call-saved register problems for exception handling. 
  > I can now run eh29.C correctly on Linux/Alpha with and without optimization;
  > a full test is underway.
Very cool.  Let me know how it goes.

It looks like they fix the regressions I got after fixing flow.c to
build a more accurate flow control graph (not yet checked in due to
the regressions).

jeff