Add an OOM adjustment category for apps undergoing backup

In this initial commit, apps undergoing backup are treated equivalently
to apps hosting services:  more important than anything other than the
foreground app.
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 9853cc6..e16a3f0 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -113,6 +113,7 @@
     setprop ro.FOREGROUND_APP_ADJ 0
     setprop ro.VISIBLE_APP_ADJ 1
     setprop ro.SECONDARY_SERVER_ADJ 2
+    setprop ro.BACKUP_APP_ADJ 2
     setprop ro.HOME_APP_ADJ 4
     setprop ro.HIDDEN_APP_MIN_ADJ 7
     setprop ro.CONTENT_PROVIDER_ADJ 14
@@ -123,6 +124,7 @@
     setprop ro.FOREGROUND_APP_MEM 1536
     setprop ro.VISIBLE_APP_MEM 2048
     setprop ro.SECONDARY_SERVER_MEM 4096
+    setprop ro.BACKUP_APP_MEM 4096
     setprop ro.HOME_APP_MEM 4096
     setprop ro.HIDDEN_APP_MEM 5120
     setprop ro.CONTENT_PROVIDER_MEM 5632