handling setjmp/longjmp in new front-end

[dewar@gnat.com]

<<What are the odds of getting Ada to use GCC's language
independant exception handling code?
>>

This is definitely on the list of things to look at, but we are not
putting it on the critical path right now.

>     The only extra restriction that I am aware of is that you cannot
>     __builtin_longjmp to a jmpbuf within the current function.

This indeed seems like a problematic restriction.