exception handling poll

[meissner@cygnus.com]

| If the .eh_frame section does not get paged into memory, then I think 10% is
| acceptable (remember that the in-memory penalty is essentially zero).  For
| kernels or embedded code where there is no paging, the acceptable figure
| is smaller, and I suspect that folks would use -fno-exceptions no matter
| how small the penalty is (unless it is 2% or less).

Some of the GCC ports I've done, even 2% is unacceptable (when you only have
32k or whatever, it does become critical not to have extra overhead).