Introduced popX method, removed useless clone in EVM abstract state

Author: VincenzoArceri

src/main/java/it/unipr/analysis/AbstractStack.java

@@ -220,6 +220,17 @@ public StackElement pop() {
 		return result;
 	}
 
+	public void popX(int pos) {
+		// Shift all elements pos position to the right
+		System.arraycopy(stack, 0, stack, pos, STACK_LIMIT - pos);
+
+		for (int i = 1; i < pos; i++)
+			if (!stack[i].isTop())
+				stack[i - 1] = StackElement.BOTTOM;
+			else
+				stack[i - 1] = StackElement.TOP;
+	}
+
 	@Override
 	public AbstractStack lubAux(AbstractStack other) throws SemanticException {
 		throw new RuntimeException("lub on abstract stack should be never called");