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>
diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
index 1f13d79..0965959 100644
--- a/src/egl/drivers/dri2/egl_dri2.c
+++ b/src/egl/drivers/dri2/egl_dri2.c
@@ -465,7 +465,10 @@
       api_mask = dri2_dpy->dri2->getAPIMask(dri2_dpy->dri_screen);
    } else {
       assert(dri2_dpy->swrast);
-      api_mask = 1 << __DRI_API_OPENGL | 1 << __DRI_API_GLES | 1 << __DRI_API_GLES2;
+      api_mask = 1 << __DRI_API_OPENGL |
+                 1 << __DRI_API_GLES |
+                 1 << __DRI_API_GLES2 |
+                 1 << __DRI_API_GLES3;
    }
 
    disp->ClientAPIs = 0;
@@ -475,6 +478,8 @@
       disp->ClientAPIs |= EGL_OPENGL_ES_BIT;
    if (api_mask & (1 << __DRI_API_GLES2))
       disp->ClientAPIs |= EGL_OPENGL_ES2_BIT;
+   if (api_mask & (1 << __DRI_API_GLES3))
+      disp->ClientAPIs |= EGL_OPENGL_ES3_BIT_KHR;
 
    assert(dri2_dpy->dri2 || dri2_dpy->swrast);
    disp->Extensions.KHR_surfaceless_context = EGL_TRUE;
@@ -737,8 +742,10 @@
          api = __DRI_API_GLES;
          break;
       case 2:
+         api = __DRI_API_GLES3;
+         break;
       case 3:
-         api = __DRI_API_GLES2;
+         api = __DRI_API_GLES3;
          break;
       default:
 	 _eglError(EGL_BAD_PARAMETER, "eglCreateContext");