Generate required parameter entity declarations in constraint modules

[drmacro]

Constraint modules that redeclare content models or attribute lists that themselves refer to named definitions (e.g., "univ-atts") must include those declarations in their entirety in the DTD version of the module because in the DTDs the base declarations of those parameter entities occur after the constraint module in the shell inclusion order.

This aspect of DTD syntax makes creating non-trivial constraint modules particularly tedious so this is an important feature to add.