Remove docs for javascript core jit configurability

This should've been removed in commit 24f10256631cd1e0f461430a50be36b74f19e01e

Task-number: QTBUG-37832

Change-Id: I3404f17c904dbb462773f40371d09b0e58a0930d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
QNX: Fix OpenGL autotest

On QNX grabbing the frame buffer returns the content of the back buffer.
In order to execute the OpenGL tests properly a swapBuffers is executed before
in order to be able to retrieve the content of the front buffer.

The patch also documents this platform behavior.

Change-Id: I7a501818ec6eea061f2f54f95854f68cb72e0534
Reviewed-by: James McDonnell <jmcdonnell@qnx.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>