Fixed normal bug EXT-6598 (Gesture pop-up menu too tall (fills height of screen))

- Limited height of gestures popup to 17 lines - 15 for gestures, 1 for label and 1 for separator. Used xml attribute "page_lines" to do it.

Reviewed by Mike Antipov at https://codereview.productengine.com/secondlife/r/199/

--HG--
branch : product-engine

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

@@ -127,6 +127,8 @@
              <gesture_combo_list.combo_button
               pad_right="10"
               use_ellipses="true" />
+             <gesture_combo_list.combo_list
+              page_lines="17" />
          </gesture_combo_list>
         </layout_panel>
 		 <icon