AMV: disable DR1 and don't override EMU_EDGE

This works around a possibly exploitable crash.
Appearently, vlc can be exploited with a malicous file. This should get
reverted as soon as a proper fix is found.

Reported-at: Thu, 21 Apr 2011 14:38:25 +0000
Reported-by: Dominic Chell <Dominic.Chell@ngssecure.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 89f903b3d5ec38c9c5d90fba7e626fa0eda61a32)
(cherry picked from commit 9b919571e506fbb72b81a35ca1e7c1bd6efc4209)
