[jdk12] adding support for the new nodes introduced for the improvements to switch statements, and the ‘switch expression’ preview feature, as well as support for the concept of preview features in general.

test/pretty/resource/before/Switch12.java

@@ -0,0 +1,30 @@
+// version 12:
+public class Switch12 {
+	public void basic() {
+		switch (5) {
+		case 1:
+		case 2:
+			System.out.println("OK");
+			break;
+		default:
+		}
+	}
+
+	public void multiCase() {
+		switch (5) {
+		case 1, 2:
+			System.out.println("OK");
+		default:
+		}
+	}
+
+	public int switchExpr() {
+		return switch (5) {
+		case 1, 2 -> 0;
+		case 3 -> {
+			break 10;
+		}
+		default -> 10;
+		} + 10;
+	}	
+}