If the user does not define YYSTYPE as a macro, Bison now declares it

	If the user does not define YYSTYPE as a macro, Bison now declares it
	using typedef instead of defining it as a macro.  POSIX requires this.
	For consistency, YYLTYPE is also declared instead of defined.

	%union directives can now have a tag before the `{', e.g., the
	directive `%union foo {...}' now generates the C code
	`typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
	The default union tag is `YYSTYPE', for compatibility with Solaris 9
	Yacc.  For consistency, YYLTYPE's struct tag is now `YYLTYPE'
	instead of `yyltype'.

	`yystype' and `yyltype' are now obsolescent macros instead of being
	typedefs or tags; they are no longer documented and will be
	withdrawn in a future release.