Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22270, verified by myself.

Switch to using lite-2's tar.h instead of ours. The contents are
identical, but lite-2's has comments explaining them, which makes it
superior to jt's tar.h. no functional difference.

Fix files using old TNF copyright notice

Add cpio.h, tar.h, and re_comp.h headers for POSIX & XPG4 conformance