Do not allow GLES 3.0 on Android

Prevented the creation of an
OpenGL ES 3.0 Context on Android.

Bug 21323928

Change-Id: I61a0972f772c8e66b57b267e1d596847063927a8
Reviewed-on: https://swiftshader-review.googlesource.com/3176
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Greg Hartman <ghartman@google.com>
Tested-by: Greg Hartman <ghartman@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>