MAJOR INTERNAL CHANGE: extend and merge operations of syntax tables
now much leaner (eliminated gramgraph, all data except tables of old
parser are shared); simplified the internal interfaces for syntax
extension;
added translations for _explode, _implode (experimental);
(*Dummy theory to document dependencies *)
Datatype = "constructor" + "inductive" + "coinductive" + Univ + QUniv
(*this must be capital to avoid conflicts with ML's "datatype" *)