tuned signature;

tuned;

plain value Keywords.keywords, which might be used outside theory for bootstrap purposes; plain value Outer_Syntax within theory: parsing requires current theory context; clarified name of Keyword.is_literal according to its semantics; eliminated pointless type Keyword.T; simplified @{command_spec}; clarified bootstrap keywords and syntax: take it as basis instead of side-branch;

proper import for command 'permanent_interpretation';