Add missing cURL constants

[haszi]

This PR adds the last few missing constants from https://github.com/php/doc-en/issues/2747. All constant descriptions and cURL version availability is based on the cURL Symbols page.

As the last commit sorts the constants which throws off the diff, this PR is definitely best reviewed commit by commit.

As a side note, I used this script to sort the constants which may or may not be useful for doing the same in the translations.