Update names of helper functions to show whether they call `send` or `put_1`/`put_2`

[jonathangjertsen]

I think this makes the code easier to read, since you can tell whether each function call will actually send some bytes over the wire or if it will just put some bytes into the buffer.

I looked at the recv part too, but it is already consistent: all functions that start with recv_ do actually call recv.

[jonathangjertsen]

send is only called by send_msg (formerly send_msg_footer), maybe it should just be one function?