This fixes the case when we pass signal to previously registered
handler, and it needs to transform the signal into different one.
Still problematic: What if the signal handler we replaced does not
terminate the application? We can end up in a weird state and loop
forever.
Possible solution: Deregister our signal handlers, CALL the previous
signal handler explicitly and if control returns, abort. This would
however complicate our code quite a bit, as we would have to parse the
sigaction we delegate to, decide whether to use signal handler or signal
action, etc...
Only some "signals" are handled under Windows, because Windows does not
use signals per-se and the mechanics are different. For now, we handle
sigsegv, stack overflow, div-by-zero and sigill. We can also
meaningfully
add various floating point errors, but not sigterm and family, because
sigterm is not a structured exception under Windows.
There is also no catch-all, because that would also catch various
debugger-related exceptions, like EXCEPTION_BREAKPOINT.
Also stops Catch from assuming its the only signal user in the binary,
and makes it restore the signal handlers it has replaced. Same goes for
the signal stack.
The signal stack itself probably shouldn't be always reallocated for
fragmentation reasons, but that can be fixed later on.
- based on PR 232 (https://github.com/philsquared/Catch/pull/232 - thanks Lukasz Forynski)
- Writes to reporter, so gets all the usual context, but then exits directly (since the stack cannot be resumed) so no summary
- On Windows does nothing, as yet.
