Skeleton backup agent for Browser

This is a skeleton backup agent for the Android Browser, intended to back up and
restore the bookmarks table from browser.db by extracting the bookmarks table
into a flattened file representation on backup, then unflattening and rebuilding
the table during restore.

It compiles but is completely untested, since the db code to read/write the
bookmarks table is not finished.  The backup agent has been declared in the
Browser manifest, however.
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 14d4bb2..2c237de 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -37,6 +37,7 @@
     <application   android:name="Browser"
                    android:label="@string/application_name"
                    android:icon="@drawable/ic_launcher_browser"
+                   android:backupAgent=".BrowserBackupAgent"
                    android:taskAffinity="android.task.browser" >
 
         <provider android:name="BrowserProvider"