remove unnecessary variables and OpenGL calls

Change-Id: Id8fb61635982681e5b16d4b4b438bb9b64c64727
small clean up in the direction of Mac support

Change-Id: I0f494db288ef0cd5d79cac82dab9088ffedff767
fix a few OpenGL resource leaks

Change-Id: I4957595d9e71c557257b7287367ee4ba689025ba
slideshow.opengl -> chart2.opengl in SAL_WARN

Change-Id: I95aa9d709110208bb3463c162ceb1fd03df20bdc
remove unnecessary variable

Change-Id: Iabd5dc6ee7511244cfefbba6d4529531f3886439
working symbol rendering based on point sprites

This approach ahs several advantages compared to the old approach. There
is no UNO involved anymore and we have a perfect shape defined by a
mathematical formula. No need for anti-aliasing or complex calculations
on the CPU.

Change-Id: I5018eae516de3368037c4c293d937de66f38568d
the msaa checks are only needed on windows

Change-Id: Ib5a4012b7365259e08e8d2fd0c1f3b239b46517c