Update copyright year in interface.c/h

Update the copyright year in interface.c and interface.h.

Signed-off-by: Rupert Muchembled <rupert@rmuch.net>
Add descriptive line to interface.c/h header

Add a short line describing the purpose of these files.

Signed-off-by: Rupert Muchembled <rupert@rmuch.net>
Update copyright year in main.c

Update the copyright year in main.c.

Signed-off-by: Rupert Muchembled <rupert@rmuch.net>