size_t is always unsigned long on OpenBSD.

Index: lib/common/pgstdinit.h
--- lib/common/pgstdinit.h.orig
+++ lib/common/pgstdinit.h
@@ -29,7 +29,7 @@ typedef unsigned long long size_t;
 #if defined(LINUX8664) || defined(TARGET_OSX_X8664) || defined(TARGET_LLVM_64)
 typedef unsigned long size_t;
 #else
-typedef unsigned size_t;
+typedef unsigned long size_t;
 #endif
 #endif
 #endif
