+/*
+ * Loop through the connections:
+ *
+ * for (c = connection_first(&i); c; c = connection_next(c, &i)) ...;
+ * connection_done(c);
+ *
+ * 'i' is the cursor, initialized by connection_first().
+ * 'c_mutex' is locked in the returned connection. The functions must
+ * be passed the previous return value so they can unlock it again.
+ */
+