The size computation was treating gigantic case expressions as
practically free, which they really aren't.  It was exacerbated by
recent decisions to charge 0 for naked variables and constructors, so
the RHS of the case might look free too.  A good example was 
Foreign.C.Error.errnoToIOError, which hsa lots of join points
that were getting inlined way to vigorously, so we had:

  *** Simplifier Phase 2 [main]:
      Result size = 2983
  *** Core Linted result of Simplifier mode 2 [main], iteration 1 out of 4:
      Result size = 640327
  *** Core Linted result of Simplifier mode 2 [main], iteration 2 out of 4:
      Result size = 1659

Notice that gigantic intermediate!

This patch adds a small charge for each *alternative*.  Of course,
that'll also mean that there's a bit less inling of things involving
case expressions.