Add missing ExpAddrOfGlobal cases.
Changed effects to a type-family implementation.

  * Allows effects to be added/subtracted in new contexts.
    * Added break back into the language.
  * Removes the need for a lot of high-ranked tom-foolery.
  * Type errors are fairly reasonable.
Make effects have a unique kind.
Type-family effects, now tracking stack allocation.
Change effect selector names, and introduce combinators
Export withBreaks.
remove withBreaks.
ivory-stdlib: new effects syntax.
ivory effects: quote type constructors-as-types, for consistency.
alpha-renaming of type variables (for more consistent error messages).
ivory: remove break type classes that aren't that useful.
ivory-stdlib: generalize effects constraint on allocs.