give lookup alert a title

xwords4/android/XWords4/res/values/strings.xml

@@ -2230,4 +2230,5 @@
     copied to the system clipboard. You can then paste them into any
     app that supports pasting text, e.g. an email app.</string>
 
+    <string name="lookup_title">Word lookup</string>
 </resources>

xwords4/android/XWords4/src/org/eehouse/android/xw4/LookupActivity.java

@@ -357,6 +357,7 @@ public class LookupActivity extends LinearLayout
         view.init( parent, bundle );
 
         Dialog result = new AlertDialog.Builder( parent )
+            .setTitle( R.string.lookup_title )
             .setView( view )
             .create();
         result.setOnKeyListener( view );