Copyright assignments and the MAINTAINERS file

[Joern Rennecke]

> We understand that sometimes it takes a while for the FSF to process 
> assignment paperwork, but we have to live with that.  Our policy is very 
> clear: no code is committed to the repository without an assignment.  We 
> do not think it's a good idea to list people in MAINTAINERS who cannot 
> contribute code.
> 
> The "Bug Database Only" accounts are an exception, and there might be 
> other exceptions.

"Code Review Only" also makes sense.  I.e. you can still me an effective
maintainer for a gcc component when you review other peoples changes.