pcre stack overflow on match

The attached table-free query causes a seg fault in 10.2.4, 10.1.21, and 10.0.21 (and presumably all the others). Setting max_recursive_iterations to various values didn't turn that into a polite error, but according to the documenation, it should have.

NOTE: setting 'thread_stack=800k' fixes this specific test, so it's definitely a stack issue. Examining a dumpfile showed many recursions of pcre 'match'.