Add functionality to allow feature mentioned in #2193.

Fix declaration of return value.

Add mapping and new menu option for octave-marking of semitones.

Finish switch case for add/remove multiple octave semitones.

Fix segfault due to illogical access using iterators from one collection on another.

Make loop more succinct.

Move PianoRoll::getAllOctavesForKey method to private access.

include/PianoRoll.h

@@ -198,6 +198,7 @@ private:
 	{
 		stmaUnmarkAll,
 		stmaMarkCurrentSemiTone,
+		stmaMarkAllOctaveSemiTones,
 		stmaMarkCurrentScale,
 		stmaMarkCurrentChord,
 		stmaCopyAllNotesOnKey
@@ -232,6 +233,8 @@ private:
 	void testPlayKey( int _key, int _vol, int _pan );
 	void pauseTestNotes(bool pause = true );
 
+	QList<int> getAllOctavesForKey( int keyToMirror ) const;
+
 	int noteEditTop() const;
 	int keyAreaBottom() const;
 	int noteEditBottom() const;