Changing top level files and include/ files over to GPLv3

[DJ Delorie]

> Changing libiberty, which is shared between projects, would have the 
> effect of changing all projects using it (bearing in mind that parts of 
> libiberty are under the GPL and parts under the LGPL, and both should 
> probably be updated at once).

Yeah, libiberty will have to be one of the last ones migrated.
Fortunately, all its files include the "or later" clause, so an
unmigrated libiberty can be used with a migrated gcc/gdb/etc.