nginx-module-modsecurity: added support for older libmaxminddb versions.

The v3.0.5 version of libmodsecurity requires at least libmaxminddb 1.4.x,
while a number of still supported platforms such as Ubuntu 18.04 "bionic",
Debian 10 "buster", or RHEL/CentOS 7/8 have quite outdated versions.

See https://github.com/SpiderLabs/ModSecurity/issues/2254 for details.