ContextMenu Support!

LLContextMenu functionality pulled out of LLPieMenu, PieMenu is now derived from LLContextMenu
- The more attribute boolean of pie_menu element determines whether or not to have an actual submenu if it's not a pie, defaults to false which means actual submenu..
-- in the future we may want to have more more="true" depending on feedback
- Pie menu labels now dynamically get " >" appended to them (avoids stupid looking context menus)
- Positioning logic combined in part, mostly conditional still, in the future we could probably combine it more.
- handleHoverOver function combines common functionality between context and pies given an item and hover mouse coords.

LiruUseContextMenus debug setting determines which to use, default is pie, of course
- Context(/Pie) Menus are rebuilt when the setting changes value
-- this is safe at any point because all startup states have been accounted for
- "Use context menus instead of pie menus" added to System->General preferences (it's close to the bottom)

indra/llui/lluictrlfactory.h

@@ -106,7 +106,7 @@ public:
 	bool builtPanel(LLPanel* panelp) {return mBuiltPanels.find(panelp->getHandle()) != mBuiltPanels.end();}
 
 	class LLMenuGL *buildMenu(const std::string &filename, LLView* parentp);
-	class LLPieMenu *buildPieMenu(const std::string &filename, LLView* parentp);
+	class LLContextMenu* buildContextMenu(const std::string& filename, LLView* parentp);
 
 	// Does what you want for LLFloaters and LLPanels
 	// Returns 0 on success