struct.pack('i', val) interprets `val` as a signed integer, and dies
if `val` > INT_MAX. For larger constants, we need to use 'I' which
interprets it as an unsigned value.
This patch makes us use 'I' for all values >= 0, and 'i' for negative
values. This should work in all cases.
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
b3cc10f3b2