[crossfire] Updating source file headers

[Kevin Zheng]

Hi there,

While poking around the sources, I realized that the headers scattered
around just about every source file need a bit of updating. Here are
some of the changes that I think should be made:

1. Let's update the header to be slightly more descriptive. While there
are many multiplayer games that aren't for X windows, there are even
more that are.

2. Bumping the copyright dates seems to be a good idea. According to
SVN, every year from 1999-2013 is a "copyrightable" year, so why not
update the headers to reflect that? The copyright is applied to the
project as a whole, not individual source files (based on my limited
knowledge of copyright law).

3. New comment style for the header. It tries to be more consistent with
headers I've seen out in the wild. There isn't really any reason for the
change other than "I like it more."

4. Maybe we can shorten the 3-paragraph GPL license? Instead, we throw
them into a top level file called LICENSE and tell users to look at that
instead. The GPLv2 usage instructions verify that this is a viable
alternative.

5. Take the $Id$ keyword out of the rcsid array if it's not being used.
We can put it as a one line comment right above/below the copyright
statement. Alternatively, we don't include it altogether.

Some of these changes may be more "controversial" than others, but I
think these are good things to change. Comments/outright objections?

Thanks,
Kevin Zheng