Beginning of struct support.

TODO:
- struct return values
- support for unions in signatures
- more testing
- complex types
- packed structs
- writing structs to buffers (useful and we have most of the machinery).

src/core/util.h

@@ -32,6 +32,7 @@
 #include <stdio.h>
 #include <errno.h>
 #include <stddef.h>
+#include <stdbool.h>
 
 #ifndef _MSC_VER
 #include <alloca.h>