Register an "ip.proto" dissector table for IPv4, and have dissectors for

Register an "ip.proto" dissector table for IPv4, and have dissectors for
protocols that run inside IPv4 register themselves with it using
"dissector_add()".

Make various dissectors static if they can be, and get rid of any header
files that no longer contain any information as a result of that change.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@1870 f5534014-38df-0310-8fa8-9805f1628bb7