- Convert many of the optimisation options into dynamic options (that is,
  they can be mentioned in {-# OPTIONS #-} pragmas).

- Add a new way to specify constructor-field unboxing on a selective
  basis.  To tell the compiler to unbox a constructor field, do this:

      data T = T !!Int

  and GHC will store that field unboxed if possible.  If it isn't possible
  (say, because the field has a sum type) then the annotation is ignored.

  The -funbox-strict-fields flag is now a dynamic flag, and has the same
  effect as replacing all the '!' annotations with '!!'.