Multiple IP discovery fixes
dr
Fixed multiple problems with IP discovery:

1.  Special data packets were being treated the same as everyone else.
Now the only data frames which undergo protocol dissection are 
TYPE_DATA and SUBTYPE_DATA.  SUBTYPE_DATA_NULL, etc, are now properly ignored.

2.  Reordered protocol fingerprinting.  If an ARP frame was long enough and had
a byte in the right position it was detected as UDP instead, and the IP copy was
totally broken.  This would result in weird almost-right (or sometimes entirely
not right) IPs.

Still gearing up for the next release Real Soon Now.