TestBPFInstruction fails with libpcap >= 1.10.2

In Debian sid, TestBPFInstruction fails with libpcap >= 1.10.2:

```
$ go test ./pcap
--- FAIL: TestBPFInstruction (0.00s)
pcap_test.go:231: Testing BpfInstruction filter 1
pcap_test.go:243: Testing dead bpf filter 1
pcap_test.go:231: Testing BpfInstruction filter 2
pcap_test.go:243: Testing dead bpf filter 2
pcap_test.go:231: Testing BpfInstruction filter 3
pcap_test.go:243: Testing dead bpf filter 3
pcap_test.go:231: Testing BpfInstruction filter 4
pcap_test.go:243: Testing dead bpf filter 4
pcap_test.go:256: expected instruction 1 = {21 0 5 34525}, got {21 0 2 2048}
pcap_test.go:256: expected instruction 2 = {48 0 0 20}, got {48 0 0 23}
pcap_test.go:256: expected instruction 3 = {21 6 0 17}, got {21 6 7 17}
pcap_test.go:256: expected instruction 4 = {21 0 6 44}, got {21 0 6 34525}
pcap_test.go:256: expected instruction 5 = {48 0 0 54}, got {48 0 0 20}
pcap_test.go:256: expected instruction 6 = {21 3 4 17}, got {21 3 0 17}
pcap_test.go:256: expected instruction 7 = {21 0 3 2048}, got {21 0 3 44}
pcap_test.go:256: expected instruction 8 = {48 0 0 23}, got {48 0 0 54}
pcap_test.go:231: Testing BpfInstruction filter 5
FAIL
FAIL github.com/google/gopacket/pcap 0.028s
FAIL
```

Manually downgrading libpcap to 1.10.1 and re-running the test passes.