libsodium 0.5.0

Closes #29254.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
Update pandoc-citeproc to 0.3.1.

Also added pandoc as a dependency, as this isn't of much use without it.
Make pandoc a recommended dependency.
pandoc-citeproc: update 0.3.1 bottle.