This patch does two main things:

1. Adjusts the way we set the Activation for

   a) The wrappers generated by the strictness analyser
      See Note [Wrapper activation] in WorkWrap

   b) The RULEs generated by Specialise and SpecConstr
      See Note [Auto-specialisation and RULES] in Specialise
          Note [Transfer activation] in SpecConstr

2. Refines how we set the phase when simplifying the right
   hand side of an InlineRule.  See
   Note [Simplifying inside InlineRules] in SimplUtils.

Most of the extra lines are comments!  

The merit of (2) is that a bit more stuff happens inside InlineRules,
and that in turn allows better dead-code elimination.