Please update rust-openssl dependency to v0.10.16

[mortebrume]

Hello.

It would be nice that you use the last rust-openssl dependency (v0.10.16) since it supports Libressl 2.9.0.

Without this, Nixes with Libressl 2.9.0 cannot build from source rust, since it relies on a rust-openssl version that doesn't support Libressl 2.9.0.

Thanks in advance.