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/standalone_scaffolding.h

@@ -42,7 +42,7 @@ _mesa_reference_shader(struct gl_context *ctx, struct gl_shader **ptr,
                        struct gl_shader *sh);
 
 extern "C" struct gl_shader *
-_mesa_new_shader(struct gl_context *ctx, GLuint name, GLenum type);
+_mesa_new_shader(struct gl_context *ctx, GLuint name, gl_shader_stage stage);
 
 extern "C" void
 _mesa_delete_shader(struct gl_context *ctx, struct gl_shader *sh);