Move components into dedicated subdirectory

This brings us a lot more tidiness.

components/entropy.c

@@ -0,0 +1,13 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+
+#include "../util.h"
+
+const char *
+entropy(void)
+{
+	int num;
+
+	return (pscanf("/proc/sys/kernel/random/entropy_avail", "%d", &num) == 1) ?
+	               bprintf("%d", num) : NULL;
+}