= XMLSimplify

The optimization passes for the <<XML#>> <<IntermediateLanguage#>> are
collected and controlled by the `XmlSimplify` functor
(https://github.com/MLton/mlton/blob/master/mlton/xml/xml-simplify.sig[`xml-simplify.sig`],
https://github.com/MLton/mlton/blob/master/mlton/xml/xml-simplify.fun[`xml-simplify.fun`]).

The following optimization passes are implemented:

* <<XMLSimplifyTypes#>>
* <<XMLShrink#>>

The optimization passes can be controlled from the command-line by the options

* `-diag-pass <pass>` -- keep diagnostic info for pass
* `-disable-pass <pass>` -- skip optimization pass (if normally performed)
* `-enable-pass <pass>` -- perform optimization pass (if normally skipped)
* `-keep-pass <pass>` -- keep the results of pass
* `-xml-passes <passes>` -- xml optimization passes
