extensions: add AMD_vertex_shader_layer

This extension will require driver support, so it must
be enabled by the driver.

http://www.opengl.org/registry/specs/AMD/vertex_shader_layer.txt

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/main/extensions.c

@@ -288,6 +288,7 @@ static const struct extension extension_table[] = {
    { "GL_AMD_draw_buffers_blend",                  o(ARB_draw_buffers_blend),                  GL,             2009 },
    { "GL_AMD_seamless_cubemap_per_texture",        o(AMD_seamless_cubemap_per_texture),        GL,             2009 },
    { "GL_AMD_shader_stencil_export",               o(ARB_shader_stencil_export),               GL,             2009 },
+   { "GL_AMD_vertex_shader_layer",                 o(AMD_vertex_shader_layer),                 GL,             2012 },
    { "GL_APPLE_object_purgeable",                  o(APPLE_object_purgeable),                  GL,             2006 },
    { "GL_APPLE_packed_pixels",                     o(dummy_true),                              GLL,            2002 },
    { "GL_APPLE_texture_max_level",                 o(dummy_true),                                   ES1 | ES2, 2009 },

src/mesa/main/mtypes.h

@@ -231,7 +231,7 @@ typedef enum
    VARYING_SLOT_CLIP_DIST0,
    VARYING_SLOT_CLIP_DIST1,
    VARYING_SLOT_PRIMITIVE_ID, /* Does not appear in VS */
-   VARYING_SLOT_LAYER, /* Appears only as GS output */
+   VARYING_SLOT_LAYER, /* Appears as VS or GS output */
    VARYING_SLOT_FACE, /* FS only */
    VARYING_SLOT_PNTC, /* FS only */
    VARYING_SLOT_VAR0, /* First generic varying slot */
@@ -3055,6 +3055,7 @@ struct gl_extensions
    GLboolean OES_standard_derivatives;
    /* vendor extensions */
    GLboolean AMD_seamless_cubemap_per_texture;
+   GLboolean AMD_vertex_shader_layer;
    GLboolean APPLE_object_purgeable;
    GLboolean ATI_envmap_bumpmap;
    GLboolean ATI_texture_compression_3dc;