Fix mips cross compile #87
                
     Merged
            
            
          
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When cross compiling on
amd64-linuxbyCGO_ENABLED=1 GOOS=linux GOARCH=mips CC=mips-linux-gnu-gcc CGO_LDFLAGS="-L/tmp/libpcap-$PCAPV" go build, this error would occur:After some investigation, the reason is that the C macro at the beginning of
pcap/pcap_unix.gofailed to definegopacket_time_secs_tandgopacket_time_usecs_tproperly.This commit fix it and it works well when cross compiling with per-compiled
libpcap.