Merge from vendor branch TNF:

Merge from vendor branch TNF:
Import p5-IO-BufferedSelect-1.0 as sysutils/p5-IO-BufferedSelect.
Based on PR#45262 by Brian De Wolf, some fixes by me.

The purpose of this module is to implement a buffered version of the select
interface that operates on lines, rather than characters. Given a set of
filehandles, it will block until a full line is available on one or more of
them.