crypt passwd length problems in 7.1 -> 7.2 upgrade

[Greg Ryan <gregr cs usyd edu au>]

After doing both an upgrade from RH 7.1 -> RH 7.2, and a from scratch
install of RH 7.2 I have found that the behaviour of authentication
against crypt passwd/shadow files has changed.

Under RH 7.1 and previous, if a password of more than 8 characters was
set, one can log in by entering the full (>8 character) password. Under
RH 7.2, if a password of more than 8 characters is set, one must log
in with exactly the first 8 characters of the password, and no more,
otherwise login is denied.

What has changed, and why?