Add missing includes

* Re-ordering Makefile.global and Makefile.mock brings in the
much-needed global CFLAGS that turn some warnings into errors
* Add missing headers to fix "missing prototype" errors
* While we're at it, properly use <> for system / standard headers

contrib/pg_upgrade/test/integration/Makefile

@@ -14,8 +14,8 @@ OBJS = scripts/gpdb5-cluster.o \
 EXS = scripts/gpdb6-cluster scripts/gpdb5-cluster
 TARGETS = greenplum_five_to_greenplum_six_upgrade_test
 
-include $(top_srcdir)/src/Makefile.mock
 include $(top_srcdir)/src/Makefile.global
+include $(top_srcdir)/src/Makefile.mock
 
 all: scripts/gpdb5-cluster scripts/gpdb6-cluster
 

contrib/pg_upgrade/test/integration/greenplum_five_to_greenplum_six_upgrade_test.c

 #include <stdarg.h>
 #include <stddef.h>
 #include <setjmp.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include <sys/stat.h>
 
 #include "cmockery.h"
 #include "libpq-fe.h"
-#include "stdbool.h"
-#include "stdlib.h"
-#include "sys/stat.h"
 
 #include "utilities/gpdb5-cluster.h"
 #include "utilities/gpdb6-cluster.h"
@@ -300,4 +302,4 @@ main(int argc, char *argv[])
 	};
 
 	return run_tests(tests);
-}
+}
\ No newline at end of file

contrib/pg_upgrade/test/integration/utilities/upgrade-helpers.c

-#include "stdlib.h"
+#include <stdio.h>
+#include <stdlib.h>
 
 /*
  * implements: