Add basic packet buffer definition

src/main.c

@@ -1,8 +1,11 @@
-#include "pupdns.h"
+#include <stdio.h>
+#include "packet_buffer.h"
 
 int main()
 {
-    printf("Hello, world!\n");
+    struct PacketBuffer *buf = new_packet_buffer();
+
+    printf("size: %ld\n", sizeof(buf->buf));
 
     return 0;
 }