Additionally to eccefd97, we need to ensure the exception handler is
installed for the _ljfault used to implement _try/_except to get called.
Also use the correct macro for x86 conditional compilation.
Addresses https://cygwin.com/ml/cygwin/2016-09/msg00143.html
Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>