App-layer proto detect cleanups

Remove unnecessay inlining.
Rename functions with wrong naming scheme. E.g. AllocAppLayer.. instead
of AppLayer..Alloc.
Use AppProto instead of uint16_t.
Convert u16 ipproto cases to u8.
Coverity 1153935: fix confusing sizeof
app-layer proto detect: optimization

Don't use FlowGetProtoMapping at runtime, use f->protomap instead.
Add safety check to make sure its value is within range, as it's
used to index an array.

Update unittests to initialized flows (somewhat).
detect: use pflow pointer

Use pflow pointer in SigMatchSignatures consistently. Also, when
needing access to the ipproto, use p->proto, not p->flow->proto.
app-layer: parser cleanup

Use f->protomap instead of calling FlowGetProtoMapping. Don't use
TcpSession *ssn ptr for anything other than TCP