Pretty printer comment drift in tag definitions

[msullivan]

The pretty printer caused the following comment drift in the ast definitions:
expr_assign(@expr /* TODO: @expr|is_lval /, @expr, ann);
became
expr_assign(@expr, / TODO: @expr|is_lval */@expr, ann);

[msullivan]

It now moves the comments in front of the types. But at least it is associated with the same tag element. Good enough.