drop use of alloca, just use malloc/free
drop use of alloca, just use malloc/free

Reported-by: Alan Coopersmith <ea3248f8c2440b9439894eab21ef26209b22bacf@oracle.com>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

patjak/xf86-video-gma500,patjak/xf86-video-gma500,wzyy2/xf86-video-modesetting,wzyy2/xf86-video-modesetting