make the application of the patch conditional (it probably breaks with Lua >= 5.2).
- Add build-with-lua51.patch to make it possible to build with Lua 5.1 (gh#editorconfig/editorconfig-core-lua!5). OBS-URL: https://build.opensuse.org/request/show/1309200 OBS-URL: https://build.opensuse.org/package/show/openSUSE:Factory/lua-editorconfig-core-lua?expand=0&rev=5