move idle news entries to its section
#16887: IDLE now accepts Cancel in tabify/untabify dialog box.
Update argparse docs to follow order of ArgumentParser() arguments.
list slotdefs in offset order rather than sorting them (closes #17610)

This means we can remove our usage of qsort() than relied on undefined behavior.

Backport by Zbigniew Halas.
#1207589: Backwards-compatibility patch for right-click menu in IDLE.
#17613: Prevent traceback when removing syntax colorizer in IDLE.