docs:  Mention SwitchCompat in Switch and toggle documentation

Bug: 19574556
Change-Id: I2ebb504b144a442d90cfdf6ab4b407726a3b896f
diff --git a/core/java/android/widget/Switch.java b/core/java/android/widget/Switch.java
index c4a1771..a01d65a 100644
--- a/core/java/android/widget/Switch.java
+++ b/core/java/android/widget/Switch.java
@@ -65,6 +65,9 @@
  * {@link #setSwitchTextAppearance(android.content.Context, int) switchTextAppearance} and
  * the related setSwitchTypeface() methods control that of the thumb.
  *
+ * <p>{@link android.support.v7.widget.SwitchCompat} is a version of
+ * the Switch widget which runs on devices back to API 7.</p>
+ *
  * <p>See the <a href="{@docRoot}guide/topics/ui/controls/togglebutton.html">Toggle Buttons</a>
  * guide.</p>
  *