Update old-style definitions to ANSI, remove a couple of register
definitions along the way. Fixed gcc 4.1 build (thank you vax)

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

Patches provided by Joel Baker in PR 22280, verified by myself.

Move the function implementations of (the non-ANSI) isascii() and toascii()
into separate modules to avoid namespace clashes.