viewer#1645 Expose RenderLocalLightCount in UI

indra/newview/skins/default/xui/en/floater_preferences_graphics_advanced.xml

@@ -102,6 +102,22 @@
     width="65">
        Low
   </text>
+  <slider
+    control_name="RenderLocalLightCount"
+    decimal_digits="0"
+    follows="left|top"
+    height="16"
+    increment="1"
+    initial_value="256"
+    label="Max. nearby lights:"
+    label_width="185"
+    layout="topleft"
+    left="30"
+    min_val="0"
+    max_val="8192"
+    name="MaxLights"
+    top_delta="16"
+    width="336" />
 
   <check_box
     control_name="RenderVSyncEnable"