nostrdb: add supporting files for the bolt11 parser

A lot of this was pulled from core-lightning. Not sure what is actually
needed or not.

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/bolt11/alignof.h

@@ -0,0 +1,20 @@
+/* CC0 (Public domain) - see LICENSE file for details */
+#ifndef CCAN_ALIGNOF_H
+#define CCAN_ALIGNOF_H
+#include "../config.h"
+
+/**
+ * ALIGNOF - get the alignment of a type
+ * @t: the type to test
+ *
+ * This returns a safe alignment for the given type.
+ */
+#if HAVE_ALIGNOF
+/* A GCC extension. */
+#define ALIGNOF(t) __alignof__(t)
+#else
+/* Alignment by measuring structure padding. */
+#define ALIGNOF(t) ((char *)(&((struct { char c; t _h; } *)0)->_h) - (char *)0)
+#endif
+
+#endif /* CCAN_ALIGNOF_H */