Assorted bugfixes:

Assorted bugfixes:
 + configuration: make sure that the NUL at the end of the config
   string is properly detected and handled, and the stats passed
   up via sysctl properly reflect which interfaces do bridging.
   (The whole config support might make good use of some cleanup
   in the future).

 + fixed some bugs related to the corruption of multicast and
   broadcast packets: make sure that for those packets the entire
   IP + ethernet header is in the mbuf, not in a cluster, so
   that writes performed in that area by the upper layers do
   not affect us.

 + performance: when calling m_pullup, make room for the ethernet header
   as well, we are going to add it in right after. Also, change an m_dup
   back to m_copypacket. The former is not necessary anymore now, and
   it did not help, anyways.

I will do a fast MFC because 95% of this patch is fixing bad bugs
and i doubt anyone would test the fix in CURRENT. Plus the last
two items mostly bring back some code which was already there in 4.0
times.