[CLEANUP] tcp: move some non tcp-specific layer6 processing out of proto_tcp

[CLEANUP] tcp: move some non tcp-specific layer6 processing out of proto_tcp

Some functions which act on generic buffer contents without being
tcp-specific were historically in proto_tcp.c. This concerns ACLs
and RDP cookies. Those have been moved away to more appropriate
locations. Ideally we should create some new files for each layer6
protocol parser. Let's do that later.