[Bug #1545726] Incorrect FSF address in many extension files.
Second round of extension executable bit cleanup. Add/remove executable bits and shebangs as appropriate. The extension entry point should be executable, while Python files that contain libraries and are not entry points should not be executable. Shebang lines should only be present in executable files.
Extensions. Import .dhw file. new code by Kevin Lindsey, Nikita Kitaev, Chris Morgan.