Revision 823030

- ozwpan: Use unsigned ints to prevent heap overflow (CVE-2015-4001)
- ozwpan: Use proper check to prevent heap overflow (CVE-2015-4002)
- ozwpan: unchecked signed subtraction leads to DoS (CVE-2015-4002)
- ozwpan: divide-by-zero leading to panic (CVE-2015-4003)