(number_suffixed): New function.
(prot_a_type): New class, with several derived classes.
(reader.error): Allow the line number to be a string, such as '*builtin*'.
(lexer.__init__): Added 'ENUMERATION-OF' to the set of builtin
	aggregates.  Add builtin types to defined_types.
(lexer): Ignore @dots{}.
(lexer.toplevel_bye): Check that all defined types are used.
(lexer.toplevel_tindex): Pass a list of the @tindex entries to
	__parse_userdefined_types, so that that function can check that
	they are all defined.
(lexer.__parse_userdefined_types): Implemented.  Several helper
	functions introduced.
(lexer.__parse_type): Simplified.  Do some error checking and
	bookkeeping.  Return a tuple, so that it is easier for the caller
	to see if an array was used.  All callers updated.
(lexer.__bad_arg): Accept "reservedX" and "flgX" for numerical values of X.
(lexer.__get_token): Handle the new tokens "::=", "|" and "=".
	Ignore comments (introduced with "!").