Defined predicate_switcher function in order to be able to use main highlighter when cursor has moved. Normally turning on this feature for the whole main highlighter is not advisable, however it is still helpful in edge cases and solves the problem with highlighting the prefix of the path and file. To prevent slowdown the predicate_switcher is defined in such a way that it activates main highlighter with respect to cursor movement just for one call, and after that returns automatically to the default mode, i.e. highlighting only after buffer is modified.