Catch and report unhandled exceptions before they propagate to C land
The C++ interface to run test cases goes like this:
1) C++ run function -> 2) C run function -> 3) C++ wrapper for
test case -> 4) test case head/body/cleanup
The previous code caught and reported unhandled exceptions in 1).
However, such approach does not seem to work everywhere. It fails,
for example, in NetBSD/i386 but works in NetBSD/amd64. I am not sure
which platform implementation is correct nor if there even _is_ a
defined behavior. No matter what, it feels wrong and clunky.
Move the last-resort exception catching to happen in 3) so that
exceptions don't propagate back to C.
Fixes the test-programs/result_test:result_exception test case in
NetBSD/i386 5.99.34.
d59f14065c