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function prototype with unspecified argument is obsolete since c99.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.

components/uptime.c

@@ -15,7 +15,7 @@
 #endif
 
 const char *
-uptime(void)
+uptime(const char *unused)
 {
 	char warn_buf[256];
 	uintmax_t h, m;