Restore audio settings and wifi.

Optimize backups by writing an entity only if the checksum of the data has changed.
Call into the hidden AudioService API to apply changed audio settings.
After restoring wifi data, make sure that the permissions and ownership are set
properly for the supplicant process to access it.
Locale isn't restoring properly - TODO added.
diff --git a/core/java/android/os/Process.java b/core/java/android/os/Process.java
index 1214abc..51e6c1e 100644
--- a/core/java/android/os/Process.java
+++ b/core/java/android/os/Process.java
@@ -68,6 +68,12 @@
     public static final int PHONE_UID = 1001;
 
     /**
+     * Defines the UID/GID for the WIFI supplicant process.
+     * @hide
+     */
+    public static final int WIFI_UID = 1010;
+
+    /**
      * Defines the start of a range of UIDs (and GIDs), going from this
      * number to {@link #LAST_APPLICATION_UID} that are reserved for assigning
      * to applications.