Update ancient copyright string in -version output

Currently the -version command line argument prints a string ending
with "Copyright (c) 2003-2008 Fabrice Bellard".  This is now some
eight years out of date; abstract it out of the several places that
print the string and update it to:

Copyright (c) 2003-2016 Fabrice Bellard and the QEMU Project developers

to reflect the work by all the QEMU Project contributors over the
last decade.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1470309276-5012-1-git-send-email-peter.maydell@linaro.org