Once this is a development branch it is not required to have such
versions.

This section is not required, it doesn't change anything.

We should not use develop at that level. Because that should not be
published like that, if you want to use the option develop, it may be
used on the highest level of buildout.cfg file.

this option was making git unusable behind a proxy

This option must be used to set the trusted certificates which gonna be
used by slapos.libnetworkcache to filter the content retrived from shadir.
It accepts multiple lines.

Well, according to the developing done in:
  - https://git.erp5.org/gitweb/slapos.libnetworkcache.git/shortlog/refs/heads/signature?js=1

It is required to build M2Crypto, otherwise it is not possible to use
the signature feature provided by slapos.libnetworkcache.

"gzip" is undefined. Not working stuff should not be in master
branch, so revert this work.
This reverts commit dcc93a3b.

Without this, system perl will be used.

Required by maatkit.

According to commit log libpng12 section was not needed, but was refered here.