GL drivers might allow using GLES3 features even in GLES2 contexts, but
that's not always the case. To make sure we can use GLES3, first try to
create a GLES3 context and then fallback to GLES2 on failure.
The reported GL version is used to determine which GLES version is
actually available.
Signed-off-by: Arnaud Vrac <avrac@freebox.fr>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Arnaud Vrac
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