Be careful to include postgres.h *before* any system headers, to ensure

that the right flavors of largefile-related definitions are seen.
Most of these changes are probably unnecessary, but better safe than
sorry.

src/backend/port/dynloader/nextstep.c

@@ -1,5 +1,8 @@
+#include "postgres.h"
+
 #include "mach-o/rld.h"
 #include "streams/streams.h"
+
 #include <stdlib.h>
 
 static char *lastError = NULL;