Clang: Cleanup more PrintTo functions

Change-Id: If1389462479ae10b067904f05cf785c3d8fb9638
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/tools/clangbackend/ipcsource/clangdocument.h

@@ -133,5 +133,5 @@ private:
 };
 
 bool operator==(const Document &first, const Document &second);
-void PrintTo(const Document &document, ::std::ostream *os);
+std::ostream &operator<<(std::ostream &os, const Document &document);
 } // namespace ClangBackEnd