swift234

implement <rdar://problem/17013042> T! <-> T? conversions should not produce a diamond 

Two pieces to this: 
 - Peephole OptionalEvaluationExpr(InjectOptionalExpr(BindOptionalExpr(X))) to  bitcast x to the result type. 
 - Enhance OptionalEvaluationExpr to delete the failure block if not needed.  

This is the same as r28150, but it includes a fix for the case when a non-address-only type
is initializing a contextally-provided-and-addressible buffer, tested by the new 
testContextualInitOfNonAddrOnlyType testcase.



Swift SVN r28153