Start removing #include directives from util/util.h.

Of course, this entails adding them to individual source files.

Change-Id: Iafa89975cfa736ac4c63559ec5e8ec88d4d97eb4
Reviewed-on: https://code-review.googlesource.com/5441
Reviewed-by: Paul Wankadia <[email protected]>
diff --git a/re2/testing/string_generator_test.cc b/re2/testing/string_generator_test.cc
index d13401a..3b5f2ea 100644
--- a/re2/testing/string_generator_test.cc
+++ b/re2/testing/string_generator_test.cc
@@ -4,9 +4,8 @@
 
 // Test StringGenerator.
 
-#include <stdlib.h>
 #include <string>
-#include <vector>
+
 #include "util/test.h"
 #include "re2/testing/string_generator.h"
 #include "re2/testing/regexp_generator.h"