We had to revert the merge of libEGL and libGLESv2 due to BC issues with
the change, so by default we no longer ship QtANGLE but the other 2
libraries.

Additionally we now mention, that the default/packaged version of Qt will
use dynamic opengl and give -opengl dynamic as an example inside the
configure documentation.

This partly reverts 7853e8e5



Change-Id: Icbf61403cd338809204fc36c6e761b03c3acd829
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>