[gdb/sim] GPLv3 switch verification

[Joel Brobecker]

Hello,

While working on switching the headers in gdb/sim to GPLv3, I noticed
some of them use formulations like "GCC is free software", or "BFD is
free software", or "The GNU simulators are free software", etc. Since
the MAINTAINERS file says that sim is part of GDB, I am planning on
switching them all to using the usual header, which says "This program
is free software; ...". (Note that a lot of files are not copyright
the FSF, so I'm not touching those files).

I hope this is OK.

-- 
Joel