st/mesa: enable ARB_explicit_attrib_location and EXT_separate_shader_objects

Gallium drivers pass all piglit tests for the two (there are 12 tests
for separate_shader_objects and 5 tests for explicit_attrib_location),
and I was told the extensions don't need any driver-specific code.

I made them dependent on PIPE_CAP_GLSL.
Signed-off-by: Brian Paul <brianp@vmware.com>

src/mesa/state_tracker/st_extensions.c

@@ -298,6 +298,8 @@ void st_init_extensions(struct st_context *st)
       ctx->Extensions.ARB_vertex_shader = GL_TRUE;
       ctx->Extensions.ARB_shader_objects = GL_TRUE;
       ctx->Extensions.ARB_shading_language_100 = GL_TRUE;
+      ctx->Extensions.ARB_explicit_attrib_location = GL_TRUE;
+      ctx->Extensions.EXT_separate_shader_objects = GL_TRUE;
    }
 
    if (screen->get_param(screen, PIPE_CAP_TEXTURE_MIRROR_REPEAT) > 0) {