fix #23543-update_accidentals



This version actually is (once more again) at moment up to date. It replaces  #1026.

The feature enables, that changing the accidental of any note is automatically valid for the whole measure from this note on.

Usage: Press the ALT-Key while performing any change of accidenteal (clicking on the symbols within the action bar, or dragging and dropping from the accidental palette, double-clicking there, or pressing the delete key to remove an accidental).