ClangFormat: Add context menu item to open current config file

Add the context menu item to C++ editor which allow you to open
the currently used .clang-format configuration file.

Change-Id: If9d6bec4f4085c18b13df15d78417aee82ddb4e4
Reviewed-by: Marco Bubke <marco.bubke@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/plugins/clangformat/clangformatutils.cpp

@@ -163,6 +163,11 @@ static QString configForFile(Utils::FileName fileName, bool checkForSettings)
     return findConfig(fileName);
 }
 
+QString configForFile(Utils::FileName fileName)
+{
+    return configForFile(fileName, true);
+}
+
 static clang::format::FormatStyle constructStyle(bool isGlobal,
                                                  const QByteArray &baseStyle = QByteArray())
 {