i965: Advertise ARB_shader_stencil_export (gen9+)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

docs/relnotes/11.1.0.html

@@ -47,6 +47,7 @@ Note: some of the new features are only available with certain drivers.
 <li>GL_ARB_blend_func_extended on freedreno (a3xx)</li>
 <li>GL_ARB_gpu_shader_fp64 on r600 for Cypress/Cayman/Aruba chips</li>
 <li>GL_ARB_gpu_shader5 on r600 for Evergreen and later chips</li>
+<li>GL_ARB_shader_stencil_export on i965 (gen9+)</li>
 <li>GL_ARB_shader_storage_buffer_object on i965</li>
 <li>GL_ARB_shader_texture_image_samples on i965, nv50, nvc0, r600, radeonsi</li>
 <li>GL_ARB_texture_barrier / GL_NV_texture_barrier on i965</li>

src/mesa/drivers/dri/i965/intel_extensions.c

@@ -358,6 +358,7 @@ intelInitExtensions(struct gl_context *ctx)
    if (brw->gen >= 9) {
       ctx->Extensions.KHR_texture_compression_astc_ldr = true;
       ctx->Extensions.KHR_texture_compression_astc_hdr = true;
+      ctx->Extensions.ARB_shader_stencil_export = true;
    }
 
    if (ctx->API == API_OPENGL_CORE)