mesa: extension boilerplate for EXT_texture_shadow_lod

With the help of Sagar, Ian and Ivan.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/glsl/glsl_parser_extras.cpp

@@ -735,6 +735,7 @@ static const _mesa_glsl_extension _mesa_glsl_supported_extensions[] = {
    EXT_AEP(EXT_texture_buffer),
    EXT_AEP(EXT_texture_cube_map_array),
    EXT(EXT_texture_query_lod),
+   EXT(EXT_texture_shadow_lod),
    EXT(INTEL_conservative_rasterization),
    EXT(INTEL_shader_atomic_float_minmax),
    EXT(MESA_shader_integer_functions),