udp-server: Mark some function arguments as unused
udp-server: Mark some function arguments as unused

After the previous commit 70ac1e9 ("udp-server/Makefile: Update compile
flags") which added -Wextra to the compile flags, introduced a bunch of
'unused parameter' warnings.

Fix these by marking the unused function parameters with
__attribute__((unused)).

For argc & argv in main(), just remove them and make main void.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@zeta.digital-domain.net>

ac000/udp-fwder