allout-kill-topic is an interactive compiled Lisp function in `
Kill topic together with subtopics.
Trailing whitespace is killed with a topic if that whitespace:
- would separate the topic from a subsequent sibling
- would separate the topic from the end of buffer
- would not be added to whitespace already separating the topic from the
Topic exposure is marked with text-properties, to be used by
`allout-yank-processing' for exposure recovery.