- remove empty useless HACKING
- remove unused cppcheck.sh
- migrate the AppImage docs to the wiki (which doesn't moan about licensing)
- try a HTML-style comment in the RELEASE docs
- since we mix Python (indentation is important) with C++ (it isn't),
having indented one-line blocks which suddenly need {} when a
statment is added is confusing and error-prone. Instead, make
the blocks explicit, always, in C++.