[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