Allow libgcj to use new exception model

[Andrew Haley]

Ach.  Grammar.

Andrew Haley writes:
 > This is needed to allow non-call exceptions (such as divide overflow
 > and SEGV) to work with the new model.  An alternative to
 > "-fnon-call-exceptions", which we may one day use on some targets, is
 > "-fcheck-references".  Only one of these is strictly necessary.

Andrew Haley means:

 > "-fnon-call-exceptions" is the defualt.  An alternative which we
 > may one day use on some targets is "-fcheck-references".

Andrew.