C++: handle case-insensitive file names in the WorkingCopy

... by keying on Utils::FileName

Task-number: QTCREATORBUG-12390
Change-Id: Ia1a59d2e422b4f92300ac6a8e0e52dd7456a6e70
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/libs/utils/fileutils.h

@@ -102,6 +102,7 @@ private:
     FileName(const QString &string);
 };
 
+QTCREATOR_UTILS_EXPORT QTextStream &operator<<(QTextStream &s, const FileName &fn);
 
 class QTCREATOR_UTILS_EXPORT FileUtils {
 public: