Sunnyvalley, Inc., is sponsoring native netmap support for the vmxnet3 adapter. This comes for free in 12, since the driver has been ported to iflib. This patch adds native support for 11 in the legacy way. To make it minimally intrusive, the native support is only enabled if vmxnet3.netmap_native is set at boot.
Tested on stable-11 running inside vmplayer.