prefer File.full_path in accordance to check_file;

more standard Thy_Load.check_thy for Pure.thy, relying on its header; pass uses and keywords from Thy_Load.check_thy to Thy_Info.load_thy; clarified 'ML_file' wrt. Thy_Load.require/provide, which is also relevant for Thy_Load.all_current;

updated Thy_Load.check_thy;