util_pcre: Restore nmatch < ncaps behaviour with PCRE1 (only).

util_pcre: Restore nmatch < ncaps behaviour with PCRE1 (only).

When the requested nmatch is below the number of captures for the regex (i.e.
nmatch is zero if the user does not care about the captures), with PCRE1 we can
pass a smaller ovector to pcre_exec() (or even NULL) which allows for somes
optimizations (less or even no recursion) internally in pcre.

This might avoid crashes due to stack usage/exhaustion with pathological
patterns (see BZ 66119).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1902732 13f79535-47bb-0310-9956-ffa450edef68