This is a half-measure until we start passing request length into the
varsize function, but it's better than the nothing we had before.

v2: Verify that there's at least a large render header's worth of
dataBytes (Julien Cristau)

v3: backport to RHEL5

v4: backport to nx-libs 3.6.x (Mike DePaulo)
Reviewed-by: Michal Srb <msrb@suse.com>
Reviewed-by: Andy Ritger <aritger@nvidia.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Fedora X Ninjas <x@fedoraproject.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

fixup swap