swift234

rework the peephole for optional-to-optional casts to be more specific.  Peepholing
on inject_into_optional/bind_optional_expr isn't safe because we don't know what 
optional_evaluation_expr is actually being bound, or if it is bound to the result of the
injection.

Instead, make this more careful to look for the evaluation_expr as well, matching
the specific pattern:
 (optional_evaluation_expr type='T?'
   (inject_into_optional type='T?'
     (bind_optional_expr type='T'
       (whatever type='T?' ...)

This fixes the two interpreter testcases that regressed in r28105.



Swift SVN r28111