replaced ML_Lex.read_antiq by more concise ML_Lex.read, which includes full read/report with explicit position information; ML_Context.eval/expression expect explicit ML_Lex source, which allows surrounding further text without loosing position information; fall back on ML_Context.eval_text if there is no position or no surrounding text; proper Args.name_source_position for method "tactic" and "raw_tactic"; tuned;

more detailed token markup, including command kind as sub_kind; type-safe access to Command.HighlightInfo;