Link `python3-config` to `python-config`

Python supplies a `python-config` command line tool to aid with finding headers, libraries, etc. Currently this is included in the package as `python${PY_VER}-config` with a link to it from `python3-config`. Would be nice to have `python-config` link to it as well. This should then mask any `python-config` coming from the system, which could cause issues for build systems that grab that one instead.