i965: Enable MESA_shader_integer_mix.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

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

@@ -157,6 +157,7 @@ intelInitExtensions(struct gl_context *ctx)
    if (brw->gen >= 5) {
       ctx->Extensions.ARB_texture_query_lod = true;
       ctx->Extensions.EXT_timer_query = true;
+      ctx->Extensions.MESA_shader_integer_mix = ctx->Const.GLSLVersion >= 130;
    }
 
    if (ctx->API == API_OPENGL_CORE)