For each link given as http://, verify that the site is accessible over
https:// and, if so, switch to it. These domains were converted:
* llvm.org
* clang.llvm.org
* en.cppreference.com
* www.dxx-rebirth.com
* www.libsdl.org
* www.scons.org
Add macro cf_assert ("control flow" assert) to hint to gcc that certain
conditions are impossible. Use it to avoid generating range checks for
situations that never happen. If the event did happen, the only
consequence would be truncated UI text, rather than a correctness
problem.
