Fixed missing way of choosing EGL renderable type with QSurfaceFormat.

Fixed missing way of choosing EGL renderable type with QSurfaceFormat.

This has been long overdue, since EGL now lets you choose between
desktop and ES based OpenGL. We also add OpenVG for those who want to
use raw OpenVG with a QOpenGLContext. The underlying EGL API for using
OpenGL / OpenVG is the same, with eglMakeCurrent() and eglSwapBuffers().

Change-Id: Ib0146b3fde5fe632069ebf99e7712f496ee7ea4d
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>