Call initializecpucache() on the BSP for i386 in the !XEN case.  This was
my bug in r271409 that I noticed while reviewing r272492.
Add netmap support to libpcap. Tcpdump and other native pcap application can now
run directly on netmap ports using netmap:foo or valeXX:YY device names.
Modifications to existing code are small and trivial, the netmap-specific
code is all in a new file.

Please be aware that in netmap mode the physical interface is disconnected from
the host stack, so libpcap will steal the traffic not just make a copy.

For the full version of the code (including linux and autotools support) see
	https://code.google.com/p/netmap-libpcap/

MFC after:	3 days