Add VPN UID to list in Process

The VPN user ID is defined in android_filesystem_config.h as 1016. Add
it to android.os.Process so it can be referred to in Java code.

Change-Id: If3da3765747afda4e5e0761e289c45eebc7cddd5
diff --git a/core/java/android/os/Process.java b/core/java/android/os/Process.java
index 6139296..770bf1c 100644
--- a/core/java/android/os/Process.java
+++ b/core/java/android/os/Process.java
@@ -98,6 +98,12 @@
     public static final int SDCARD_RW_GID = 1015;
 
     /**
+     * Defines the UID/GID for the group that controls VPN services.
+     * @hide
+     */
+    public static final int VPN_UID = 1016;
+
+    /**
      * Defines the UID/GID for the NFC service process.
      * @hide
      */