makefile: fix documentation The only available rules is 'deb-prepare' we fix the documentation.

tests: use curl instead of wget curl is supplied by default on macOS 10.12, but wget isn't. As curl is easy to install on other OSes, just switch the tests over. For Windows systems, you can obtain cURL from https://curl.haxx.se/download.html - for other systems, please use your native package manager. This undoes 4e7da688a066 and 3ffa12edc05a, as they don't make things much simpler on Windows (you have to install extra packages either way round), but they do make things harder on macOS (as curl is supplied by default, whereas wget isn't).