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function prototype with unspecified argument is obsolete since c99.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/entropy.c

@@ -7,7 +7,7 @@
 	#include "../util.h"
 
 	const char *
-	entropy(void)
+	entropy(const char *unused)
 	{
 		uintmax_t num;
 
@@ -20,7 +20,7 @@
 	}
 #elif defined(__OpenBSD__) | defined(__FreeBSD__)
 	const char *
-	entropy(void)
+	entropy(const char *unused)
 	{
 		/* Unicode Character 'INFINITY' (U+221E) */
 		return "\xe2\x88\x9e";