Moved inst module to lib

As it has no dependencies on vm specifically, and it's more necessary
for any vendors who wish to target the virtual machine, it makes more
sense for inst to be a lib module rather than a vm module.

vm/main.c

@@ -14,8 +14,8 @@
 #include <stdio.h>
 #include <string.h>
 
-#include "./inst.h"
 #include "./runtime.h"
+#include <lib/inst.h>
 
 int interpret_bytecode(const char *filepath)
 {