Passing data in sql_yacc.yy through LEX members is hard to follow and is not recursively safe.
We'll get rid of LEX::length and LEX::dec and add a structure instead:
so it can be passed through the syntax rules in sql_yacc.yy as $$, $1, $2, etc.
This will help, for example, to change:
So we'll already know data type, length and dec when we do "new Create_field".
This will allow to call a method in Type_handler, to create a data-type specific "Create_field" replacement, instead of using the generic universal Create_field.