af-packet: optimize BPF

This patch turn on code optimization on BPF filter building by
libpcap. This allow to reduce the size of the BPF bytecode and
thus increase the size of BPF filter supported by Suricata.

Reported-by: Martijn van Oosterhout

src/source-af-packet.c

@@ -2085,7 +2085,7 @@ TmEcode AFPSetBPFFilter(AFPThreadVars *ptv)
                 ptv->datalink,    /* linktype_arg */
                 &filter,       /* program */
                 ptv->bpf_filter, /* const char *buf */
-                0,             /* optimize */
+                1,             /* optimize */
                 0              /* mask */
                 ) == -1) {
         SCLogError(SC_ERR_AFP_CREATE, "Filter compilation failed.");