do not rely on obsolete feature

function prototype with unspecified argument is obsolete since c99.

additionally some of these function which don't take any argument were
being called with a `const char *` arg, which is UB.

fix both these issues by declararing ALL the components to accept a
`const char *`, and name the arg "unused" if it's meant to be ignored.

config.mk

@@ -12,7 +12,7 @@ X11LIB = /usr/X11R6/lib
 
 # flags
 CPPFLAGS = -I$(X11INC) -D_DEFAULT_SOURCE
-CFLAGS   = -std=c99 -pedantic -Wall -Wextra -Os
+CFLAGS   = -std=c99 -pedantic -Wall -Wextra -Wno-unused-parameter -Os
 LDFLAGS  = -L$(X11LIB) -s
 # OpenBSD: add -lsndio
 # FreeBSD: add -lkvm -lsndio