scripts/qemu-gdb/timers.py: define encoding in header comment

This is required otherwise python complains because of the
accentuated letter in Alex's last name:

Traceback (most recent call last):
  File "scripts/qemu-gdb.py", line 29, in <module>
    from qemugdb import aio, mtree, coroutine, tcg, timers
  File "scripts/qemugdb/timers.py", line 1
SyntaxError: Non-ASCII character '\xc3' in file scripts/qemugdb/timers.py
 on line 1, but no encoding declared;
 see http://www.python.org/peps/pep-0263.html

 for details

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <151629549711.18276.15497684562308683805.stgit@bahia.lan>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>