Makes gtest_break_on_failure_unittest work on minGW (by vladl); improves

the NULL-dereferencing hack to work with LLVM (by chandlerc).

src/gtest.cc

@@ -3608,7 +3608,11 @@ void UnitTest::AddTestPartResult(TestPartResult::Type result_type,
       // the --gtest_catch_exceptions flags are specified.
       DebugBreak();
 #else
-      *static_cast<int*>(NULL) = 1;
+      // Dereference NULL through a volatile pointer to prevent the compiler
+      // from removing. We use this rather than abort() or __builtin_trap() for
+      // portability: Symbian doesn't implement abort() well, and some debuggers
+      // don't correctly trap abort().
+      *static_cast<volatile int*>(NULL) = 1;
 #endif  // GTEST_OS_WINDOWS
     } else if (GTEST_FLAG(throw_on_failure)) {
 #if GTEST_HAS_EXCEPTIONS