Replace OpKill With function call. (#2790)

We are no able to inline OpKill instructions into a continue construct.
See #2433.  However, we have to be able to inline to correctly do
legalization.  This commit creates a pass that will wrap OpKill
instructions into a function of its own.  That way we are able to inline
the rest of the code.

The follow up to this will be to not inline any function that contains
an OpKill.

Fixes #2726