getChosenGLCapabilities may return null before GLListener init.

Store capabilities at a safe location inside PGLListener init.

Signed-off-by: Xerxes Rånby <xerxes@zafena.se>
Fix PGLListener init extension checks to pass on OpenGL ES 2.

Signed-off-by: Xerxes Rånby <xerxes@zafena.se>
Validate PApplet AWT Container after add of OpenGL canvas.

This fix a long startup delay before OpenGL init
that may happen if the OpenGL canvas stay non-visible.

Signed-off-by: Xerxes Rånby <xerxes@zafena.se>