egl/dri2: Add plumbing for EGL_OPENGL_ES3_BIT_KHR

egl/dri2: Add plumbing for EGL_OPENGL_ES3_BIT_KHR

Fixes error EGL_BAD_ATTRIBUTE in the tests below on Intel Sandybridge:
    * piglit egl-create-context-verify-gl-flavor, testcase OpenGL ES 3.0
    * gles3conform, revision 19700, when runnning GL3Tests with -fbo

This plumbing is added in order to comply with the EGL_KHR_create_context
spec. According to the EGL_KHR_create_context spec, it is illegal to call
eglCreateContext(EGL_CONTEXT_MAJOR_VERSION_KHR=3) with a config whose
EGL_RENDERABLE_TYPE does not contain the EGL_OPENGL_ES3_BIT_KHR. The
pertinent
portion of the spec is quoted below; the key word is "respectively".

  * If <config> is not a valid EGLConfig, or does not support the
    requested client API, then an EGL_BAD_CONFIG error is generated
    (this includes requesting creation of an OpenGL ES 1.x, 2.0, or
    3.0 context when the EGL_RENDERABLE_TYPE attribute of <config>
    does not contain EGL_OPENGL_ES_BIT, EGL_OPENGL_ES2_BIT, or
    EGL_OPENGL_ES3_BIT_KHR respectively).

To create this patch, I searched for all the ES2 bit plumbing by calling
`git grep "ES2_BIT\|DRI_API_GLES2" src/egl`, and then at each location
added a case for ES3.

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>