Apply the kind subst to the (kinds of the) quanitifed tyvars in deriveTyData

I've elaboated Note [Unify kinds in deriving] to explain
what is going on here.

The change fixes Trac #8893.
Simplify handling of the interactive package; fixes Trac #8831

This patch is really a fix to the big commint
   73c08ab10e4077e18e459a1325996bff110360c3
   Re-work the naming story for the GHCi prompt (Trac #8649)
which introduced the 'interactive' package
See Note [The interactive package] in HscTypes

The original commit set both
  (a) The tcg_mod field of TcGblEnv to 'interactive:Ghci4' (say)
  (b) The thisPackage field of DynFlags to 'interactive'

But the second step interacts badly with linking.  :loaded modules are
in the package set by 'thisPackage' (usually 'main'); if you change
that, then we try to link package 'main', but can't find it, and
that is what happened in #8831.

The fix was simple: do (a) but not (b).

I changed Note [The interactive package] in HscTypes to describe this.
Test Trac #8893
Trac #8831 is fixed