Revert "Remove opengl usage from svx until we can't solve building problems"

This reverts commit 10be411f33c69db83cc5de410eaddf2d297608ae.
prevent initializing the OpenGL context multiple times

Change-Id: I2ebdbcd51938bc1dc61693ac392eed5d5e497a8d
fix crash when passing external Window to OpenGLContext::init

The external window is not controlled by OpenGLContext so it is not
allowed to delete the window

Change-Id: Id2c79a3612cc875fd94b8cd1206b30af2f185875