Apply @hide / @SystemApi to android.telecom.*

Move the android.telecom.* namespace back to @hide, and also mark it
with @SystemApi so that system-privileged apps can use them.

Bug: 18302450
Change-Id: I33ae1b9b0dfdb1c5eff51ca3c829196bcfc9411c
diff --git a/telecomm/java/android/telecom/GatewayInfo.java b/telecomm/java/android/telecom/GatewayInfo.java
index 7105602..5b8e4ab 100644
--- a/telecomm/java/android/telecom/GatewayInfo.java
+++ b/telecomm/java/android/telecom/GatewayInfo.java
@@ -34,7 +34,9 @@
  * <li> Call the appropriate gateway address.
  * <li> Display information about how the call is being routed to the user.
  * </ol>
+ * @hide
  */
+@SystemApi
 public class GatewayInfo implements Parcelable {
 
     private final String mGatewayProviderPackageName;