[DISCUSS] code freeze 3.5.3/3.6.0

[Stephen Mallette]

I should have sent this a bit earlier but I think we largely have all of
the PRs in review at this point that will cover what was planned for 3.5.3
and 3.6.0. As such I think we can enter into code freeze for close of
business tomorrow and get organized for release. Please yell if there are
any outstanding concerns to address.