Closes #13867: remove untrue comment about PyWeakref_Check().
Issue #18037: Do not escape '\u' and '\U' in raw strings.
merge heads
Add "->" as a delimiter token.  Found by James Harding on docs@.
Fix wrong link.
Clarify two points about division and shifting. Suggested by Albert Hofkamp on docs@.
Minor grammar fix.
Issue 19158:  a rare race in BoundedSemaphore could allow .release() too often.