kingst-la2016: rephrase sample data to session feed logic

kingst-la2016: rephrase sample data to session feed logic

Comment on the layout of the incoming captured data for awareness during
maintenance. Rephrase the send_chunk() routine for improved readability.
Eliminate too short i, j, k variables. Comment on the non-obvious flush
condition for the conversion buffer. Prefer "sample" in variable names
to not confuse captures with the device's run state. Eliminate another
literal 2 which slipped through in an earlier commit. Adjust data types.