nostrdb: ccan: copy ccan files into their own subdirectory.

This lets them be updated/bugfixed together.  I just copied them for now,
didn't change anything else.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/ccan/ccan/list/list.c

@@ -0,0 +1,43 @@
+/* Licensed under BSD-MIT - see LICENSE file for details */
+#include <stdio.h>
+#include <stdlib.h>
+#include "list.h"
+
+static void *corrupt(const char *abortstr,
+             const struct list_node *head,
+             const struct list_node *node,
+             unsigned int count)
+{
+    if (abortstr) {
+        fprintf(stderr,
+            "%s: prev corrupt in node %p (%u) of %p\n",
+            abortstr, node, count, head);
+        abort();
+    }
+    return NULL;
+}
+
+struct list_node *list_check_node(const struct list_node *node,
+                  const char *abortstr)
+{
+    const struct list_node *p, *n;
+    int count = 0;
+
+    for (p = node, n = node->next; n != node; p = n, n = n->next) {
+        count++;
+        if (n->prev != p)
+            return corrupt(abortstr, node, n, count);
+    }
+    /* Check prev on head node. */
+    if (node->prev != p)
+        return corrupt(abortstr, node, node, 0);
+
+    return (struct list_node *)node;
+}
+
+struct list_head *list_check(const struct list_head *h, const char *abortstr)
+{
+    if (!list_check_node(&h->n, abortstr))
+        return NULL;
+    return (struct list_head *)h;
+}