Update stale pg_config.h.in

Shouldav been part of commit 83147222 that adds execinfo.h for
OpenBSD.
Co-authored-by: NJesse Zhang <sbjesse@gmail.com>
Co-authored-by: NAlexandra Wang <lewang@pivotal.io>

src/include/pg_config.h.in

@@ -172,6 +172,9 @@
 /* Define to 1 if you have the <event.h> header file. */
 #undef HAVE_EVENT_H
 
+/* Define to 1 if you have the <execinfo.h> header file. */
+#undef HAVE_EXECINFO_H
+
 /* Define to 1 if you have the `fcvt' function. */
 #undef HAVE_FCVT
 
@@ -344,6 +347,9 @@
 /* Define to 1 if you have the `crypto' library (-lcrypto). */
 #undef HAVE_LIBCRYPTO
 
+/* Define to 1 if you have the `execinfo' library (-lexecinfo). */
+#undef HAVE_LIBEXECINFO
+
 /* Define to 1 if you have the `gpdbcost' library (-lgpdbcost). */
 #undef HAVE_LIBGPDBCOST
 
@@ -810,6 +816,9 @@
 /* PostgreSQL major version as a string */
 #undef PG_MAJORVERSION
 
+/* Define to gnu_printf if compiler supports it, else printf. */
+#undef PG_PRINTF_ATTRIBUTE
+
 /* Define to 1 if "static inline" works without unwanted warnings from
    compilations where static inline functions are defined but not called. */
 #undef PG_USE_INLINE