[clang-rename] Fix handling of unchanged files

Fix the output of clang-rename for the files without modifications.
Update the code in clang-reorder-fields/tool/ClangReorderFields.cpp 
to avoid inconsistency.

Example:
a.h:
struct A {};
a.cpp:
#include "a.h"
int main() { return 0; }

Before the changes the output looks like this:
clang-rename -qualified-name=A -new-name=B a.cpp
<<<<<INVALID SOURCE LOCATION>>>>>

Test plan: make -j8 check-clang-tools

Differential revision: https://reviews.llvm.org/D24634

llvm-svn: 281826
diff --git a/clang-tools-extra/test/clang-rename/IncludeHeaderWithSymbol.cpp b/clang-tools-extra/test/clang-rename/IncludeHeaderWithSymbol.cpp
new file mode 100644
index 0000000..cb2baee
--- /dev/null
+++ b/clang-tools-extra/test/clang-rename/IncludeHeaderWithSymbol.cpp
@@ -0,0 +1,10 @@
+#include "Inputs/HeaderWithSymbol.h"
+
+int main() {
+  return 0; // CHECK: {{^  return 0;}}
+}
+
+// Test 1.
+// The file IncludeHeaderWithSymbol.cpp doesn't contain the symbol Foo
+// and is expected to be written to stdout without modifications
+// RUN: clang-rename -qualified-name=Foo -new-name=Bar %s -- | FileCheck %s