This change removes some stale behavior

The old version of the _defaultOf function for default-sized reals and imags
wanted a cast, because it was specifying the default size rather than just using
it automatically.  With that change, the cast is unnecessary.
Merge pull request #333 from lydia-duncan/removeUnnecessaryCast

This change removes some stale behavior [suggested/reviewed by bradc]

The old version of the _defaultOf function for default-sized reals and imags
wanted a cast, because it was specifying the default size rather than just using
it automatically. With that change, the cast is unnecessary.