* the rendering now consits of two panes
- the background pane (for animated stuff like the map)
- the foreground pane (for steady stuff, like UI)
each pane has it own max FPS and works idependently
this may increase graphics performance on many platforms
* option to pass -opengl1 or -opengl2 as argument
* note that with this commit there are a lot of graphics regressions and the master will remaing unstable for a while
* shaders disabled for a while
* implement draw clipping using opengl stencil buffers
* allow to create Widgets by style name with g_ui.createWidgetByStyle
* styles can now have children widgets
* make proper use of the isNotPathable in pathfinding
* add scrollbar skin
Eduardo Bart