Update the pcre recursion limit test

This test had been disabled before to reduce the maintenance burdon, but
I think it really should be possible to find a regex & pattern to
reliably run into PCRE_ERROR_RECURSIONLIMIT / PCRE_ERROR_JIT_STACKLIMIT.
And it seems that the work to find such a regex & pattern had already
been done for us. :)

Looking after the test made me realize that we really should consider
latching VCL failure for "hard" pcre errors.

This commit is to have a diff in the git log, the next commit will
activate the test.