[PATCH-revised^6] common test code for timed bail

The attached patch addresses the following Perl TODO:

=head2 common test code for timed bail out

Write portable self destruct code for tests to stop them burning CPU in
infinite loops. This needs to avoid using alarm, as some of the tests are
testing alarm/sleep or timers.

(Typo correction)

• [PATCH-revised^6] common test code for timed bail by Jerry D. Hedden
• Re: [PATCH-revised^6] common test code for timed bail by Rafael Garcia-Suarez