wordcolor: Add 'systemd' to the system color group

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Use 'chtype' when working with ncurses colors

To silence a compile-time warning, use chtype instead of int when
working with ncurses colors.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Warning fixes

Add a few __attribute__((unused)) declarations, and clean up the code so
it produces no warnings with -Wall -Wextra.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Simplify the compiler warning flags

Instead of having a huge list of custom compiler warning flags, use
-Wall -Wextra only.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>