Reverse order of KJ_MAP to be consistent with e.g. KJ_IF_MAYBE.
Warn when an optimized build doesn't set NDEBUG and then #define it ourselves -- unless the build explicitly sets DEBUG.
Enable more warnings and -Werror in test script, fix problems.
Don't allow releases when TODO(now) or TODO(soon) or KJ_DBG are found in the code.
Update sample code for new union syntax.
Add -f flag to ln so that installing over an existing install doesn't fail.