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/debug.h

@@ -0,0 +1,15 @@
+
+#ifndef PROTOVERSE_DEBUG_H
+#define PROTOVERSE_DEBUG_H
+
+#include <stdio.h>
+
+#define unusual(...) fprintf(stderr, "UNUSUAL: " __VA_ARGS__)
+
+#ifdef DEBUG
+#define debug(...) printf(__VA_ARGS__)
+#else
+#define debug(...)
+#endif
+
+#endif /* PROTOVERSE_DEBUG_H */