.clang-format overrides tab size

The whole point of using tabs is to let everyone set their desired visual indent width. This mode can be achieved in clang-format with the 'UseTab: AlignWithSpaces' setting. However, QtC always takes tab width from .clang-format and overrides the editor settings, defeating the whole purpose of using tabs for indentation. Please add an option to avoid that (or, better yet, an option to follow .clang-format settings).