Make x-deltat.y work with bison 3

[Reviewers probably want to look only at the changes to x-deltat.y, not the changes to the generated deltat.c.]

Bison 3 removed support for YYPARSE_PARAM and YYLEX_PARAM, breaking
x-deltat.y.  Use %parse-param and %lex-param instead.  (In Bison 3 we
could use just %param, but that doesn't work in 2.x.)  The parameter
added by %parse-param is also passed to yyerror, so adjust the macro
we use to suppress yyerror accordingly.

Also use "%define api.pure" instead of "%pure_parser", which was
deprecated in bison 2.3b.  (The correct spelling was actually
"%pure-parser", and bison 3 generates a warning about the underscore
spelling.)

Regenerate deltat.c using the new x-deltat.y and bison 3.0.2.