libxt_policy: use bounded strtoui

reqid and SPI can only have a value in the range 0..UINT32_MAX, not
the entire range of the "long" type. Also throw an error if the
incoming string does not look like a pure number.

"Replaces" commit 6db2ded2f22a7e78743c86af523b8430876582e9.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
2 files changed