Print for-alls more often (Trac #9018)

We now display the foralls of a type if any of the type variables
is polykinded.  This put kind polymorphism "in your face" a bit more
often, but eliminates a lot of head scratching.

The user manual reflects the new behaviour.

(cherry picked from commit 2f3ea952)

Conflicts:
	testsuite/tests/ghci/scripts/ghci059.stdout
	testsuite/tests/polykinds/T7438.stderr