i915: Accept GL_DEPTH_STENCIL GL_DEPTH_COMPONENT formats for renderbuffers

Gen2 doesn't support depth/stencil textures, and since

 commit c1d4d499
 Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
 Date:   Thu Apr 24 14:11:43 2014 +0300

    i915: Don't advertise Z formats in TextureFormatSupported on gen2

depth/stencil formats are no longer accepted as texture formats.
However we still want depth/stencil renderbuffers, so add explicit
format checks to intel_alloc_renderbuffer_storage() to allow such
things.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

src/mesa/drivers/dri/i915/intel_fbo.c

@@ -180,6 +180,15 @@ intel_renderbuffer_format(struct gl_context * ctx, GLenum internalFormat)
       return intel->ctx.Driver.ChooseTextureFormat(ctx, GL_TEXTURE_2D,
                                                    internalFormat,
                                                    GL_NONE, GL_NONE);
+
+   case GL_DEPTH_COMPONENT16:
+      return MESA_FORMAT_Z_UNORM16;
+   case GL_DEPTH_COMPONENT:
+   case GL_DEPTH_COMPONENT24:
+   case GL_DEPTH_COMPONENT32:
+      return MESA_FORMAT_Z24_UNORM_X8_UINT;
+   case GL_DEPTH_STENCIL_EXT:
+   case GL_DEPTH24_STENCIL8_EXT:
    case GL_STENCIL_INDEX:
    case GL_STENCIL_INDEX1_EXT:
    case GL_STENCIL_INDEX4_EXT: