Add a regression test for a fixed strnlen bug.

Bug: https://code.google.com/p/android/issues/detail?id=74741
Change-Id: I78b0114bdbe8e680b0e938af608a634e73c86eda

tests/string_test.cpp

@@ -22,6 +22,7 @@
 #include <gtest/gtest.h>
 #include <malloc.h>
 #include <math.h>
+#include <stdint.h>
 
 #include "buffer_tests.h"
 
@@ -1396,6 +1397,10 @@ TEST(string, strnlen_147048) {
   delete[] heap_src;
 }
 
+TEST(string, strnlen_74741) {
+  ASSERT_EQ(4U, strnlen("test", SIZE_MAX));
+}
+
 TEST(string, mempcpy) {
   char dst[6];
   ASSERT_EQ(&dst[4], reinterpret_cast<char*>(mempcpy(dst, "hello", 4)));