Made darwin_hotplug_poll static to fix Xcode warning

Signed-off-by: Nathan Hjelm <hjelmn@me.com>
Fixed clang static analyzer warning about dereferencing null

It looks like *ifcp should be the same as iface,
so I just use the latter instead of the former.

Closes pull request #13

Signed-off-by: Nathan Hjelm <hjelmn@me.com>