Optimize Debian fpm size

[Anastasios89]

Debian fpm docker size is huge compare to alpine,
This request removes PHPIZE_DEPS from docker.
Docker size reduces to almost on half.

[tianon]

Duplicate of #438

see discussion there for why this won't be accepted, especially #438 (comment)

[Anastasios89]

If users want to install $PHPIZE_DEPS, they can do it manually before configure and install and they can delete whatever package afterwards. Keeping a "dirty" layer with dev tools on a production docker image is not handy and quite silly. We use docker for production, not for fun. Upload/download/store multiple instances of a dirty docker images is costly. After all if some users cannot handle apt-get correctly, it's not a bug. Thanks for your time