mesa/glsl: stop using GL shader type internally

Instead use the internal gl_shader_stage enum everywhere. This
makes things more consistent and gets rid of unnecessary
conversions.

Ideally it would be nice to remove the Type field from gl_shader
altogether but currently it is used to differentiate between
gl_shader and gl_shader_program in the ShaderObjects hash table.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/glsl/linker.cpp

@@ -2235,7 +2235,7 @@ link_intrastage_shaders(void *mem_ctx,
       return NULL;
    }
 
-   gl_shader *linked = ctx->Driver.NewShader(NULL, 0, main->Type);
+   gl_shader *linked = ctx->Driver.NewShader(NULL, 0, shader_list[0]->Stage);
    linked->ir = new(linked) exec_list;
    clone_ir_list(mem_ctx, linked->ir, main->ir);