Cancel dive edit when escape key is pressed

Also seems intuitive. What's odd is that in the Planner you get a
confirmation dialog while here you don't. We should be consistent.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/maintab.h

@@ -82,6 +82,7 @@ slots:
 	void toggleTriggeredColumn();
 	void updateTextLabels(bool showUnits = true);
 	QString trHemisphere(const char *orig);
+	void escDetected(void);
 
 private:
 	Ui::MainTab ui;