[Gtk-sharp-list] Copyright on generated files

[fd]

Right now, C# sources generated by Gtk# get the header:

// Generated File.  Do not modify.
// <c> 2001-2002 Mike Kestner

It would seem more sensible to leave the generated code without a
license, or to mark files explicitly as being in the public domain to
avoid legal ambiguity for the resultant binaries.

The "Generated file" notice should probably remain as a warning.
However, "Do not modify" reads far too much like an obnoxious licensing
clause and is in need of rephrasing.