add the extra functions for drawing gui elements
RoundedRectangle:
All draw rect functions now pass through roundedRectangle which uses a shader and can draw borders, and rounds the corners
Draw thick line:
draws a line thicker than 1 pixel, uses a geometry shader to do this
Draw Circle:
Draws a circle with a border parameter.
demonstrates a bit of usage in guibitmapctrl. (do note, gui elements may need followup via altering thier clip rect depending on how folks want to end up using this)
