Fix broken tests after migration back to C.

Most of the errors were initialization related, however the -Wall
flag was missing, and there were two functions not returning that
were nonvoid.
All tests passing after migration back to C.

Packet tests still not complete at this point.
Add size helper.

Added a function to determine the serialized size of the rtp
packet.
Added rtp return type.

This type will essentially contain all the return codes for the
library.  Longer term, I will add a string printer for better
debugging.  In general, I hate typedefs, but in this case it should
be useful.
Packet api implemented.

Still need tests for serialization.