Do something about the lrexlib-PCRE dependency hell

[rulatir]

Please do something about the lrexlib-PCRE dependency. I am trying to build a docker image from openresty including this module, and it's giving me hell, severely limiting the choice of base image versions. For openresty:stretch, I must install luarocks and lipcre3(-dev). For openresty:bionic, I havent figured out a working solution yet: luarock errors out if I install it from repo so I can't use that, and while there is lua-rex-pcre in the repo, installing it doesn't help since openresty's embedded lua fails to "see" it and errors out on "rex_pcre module required".