Revert "ChangeLogs: convert to utf-8"

Revert "ChangeLogs: convert to utf-8"

This reverts commit d2bb040b2a2f58b1ef80f01292bd722fce01d36a.

It seems some files (like tst-regex) directly parse these and rely on
some of its content *not* being UTF-8.  Until we can fix thoses tests
(and isolate them from ChangeLog updates), back out this change.

It also shouldn't really have landed during the freeze.