Parse: MS property members cannot have an in-class initializer

We would crash trying to treat a property member as a field.  These
shoudl be forbidden anyway, reject programs which contain them.

This fixes PR21840.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@224193 91177308-0d34-0410-b5e6-96231b3b80d8