Invalid copyright not detected

`[C] The Regents of the University of Michigan and Merit Network, Inc. 1992,
1993, 1994, 1995 All Rights Reserved` is rare and not detected because `[C]` is not a valid copyright "sign"

We have a few other cases in https://github.com/search?q="Copyright+[C]"&type=code

The only sane resolution I can think of is to normalize these warts in text preparation:
- replace `[C] The Regents of the University` by `(C) The Regents of the University`
- replace `Copyright [c]` by `Copyright (c)` in all character cases.

`[C]` cannot be/is not a valid sign and this would otherwise trigger a badzillion of false positives as seen in https://github.com/search?q="[C]"&type=code (actually only millions, not badzillions)