Don't try to save the assigned value in a Objective-C property assignment
if the type of the value is a non-trivial class type.  Fixes PR14318.

(There's a minor ObjC++ language change here: given that we can't save the
value, the type of the assignment expression is void in such cases.)



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167884 91177308-0d34-0410-b5e6-96231b3b80d8