Make include files work without having to include other ones first

Author: petere

src/include/access/hio.h

@@ -14,6 +14,7 @@
 #ifndef HIO_H
 #define HIO_H
 
+#include "access/heapam.h"
 #include "access/htup.h"
 #include "utils/relcache.h"
 #include "storage/buf.h"

src/include/utils/json.h

@@ -15,6 +15,7 @@
 #define JSON_H
 
 #include "fmgr.h"
+#include "lib/stringinfo.h"
 
 extern Datum json_in(PG_FUNCTION_ARGS);
 extern Datum json_out(PG_FUNCTION_ARGS);