cpp-131: Long tap on erase button should remove text faster

Fixes #131

core/src/main/java/org/solovyev/android/calculator/Calculator.java

@@ -64,6 +64,8 @@ public interface Calculator extends CalculatorEventContainer, HistoryControl<Cal
 								 @Nonnull String expression,
 								 @Nonnull Long sequenceId);
 
+	void setCalculateOnFly(boolean calculateOnFly);
+
 	boolean isCalculateOnFly();
 
 	/*

core/src/main/java/org/solovyev/android/calculator/CalculatorImpl.java

@@ -207,8 +207,14 @@ public class CalculatorImpl implements Calculator, CalculatorEventListener {
 		Locator.getInstance().getHistory().load();
 	}
 
+	@Override
 	public void setCalculateOnFly(boolean calculateOnFly) {
-		this.calculateOnFly = calculateOnFly;
+		if (this.calculateOnFly != calculateOnFly) {
+			this.calculateOnFly = calculateOnFly;
+			if (this.calculateOnFly) {
+				evaluate();
+			}
+		}
 	}
 
 	@Override

core/src/main/java/org/solovyev/android/calculator/CalculatorSpecialButton.java

@@ -169,7 +169,7 @@ public enum CalculatorSpecialButton {
 	};
 
 	@Nonnull
-	private static Map<String, CalculatorSpecialButton> buttonsByActionCodes = new HashMap<String, CalculatorSpecialButton>();
+	private static Map<String, CalculatorSpecialButton> buttonsByActionCodes = new HashMap<>();
 
 	@Nonnull
 	private final String actionCode;