Also use https:// instead of git:// when possible

(Make the build more resistant against MITM attacks, part 2)

git://git.kernel.org -> https://git.kernel.org
git://github.com     -> https://github.com

Thanks for applying the last fix so fast! This can also be applied right away to both repos. I had forgotten to grep for git://, sorry.

However, all the people who have previously cloned from a git://github.com URL as per the instructions will still have that in their repo copy's .git/config. I'm not sure what to do about that. Put a warning somewhere? Modify the scripts to run sed on .git/config?