[v3] add -fno-exceptions support

[Jason Merrill]

>>>>> "Benjamin" == Benjamin Kosnik <bkoz@redhat.com> writes:

>> It sounds like libsupc++ only needs the macros
>> (try/catch/__throw_exception_again) from that header, right?

> Right. So, just move the header into libsupc++? Or just define the same 
> macro bits in those files? Probably moving the header into libsupc++ is 
> better.

> Or we could just have a header with those defines, and have it be in 
> libsupc++ and functexcept.h could include that header.  That might be
> best.

Works for me.

Jason