[MSVC] 'property' with an empty array in array subscript expression.

MSVC supports 'property' attribute and allows to apply it to the declaration of an empty array in a class or structure definition.
For example:
```
__declspec(property(get=GetX, put=PutX)) int x[];
```
The above statement indicates that x[] can be used with one or more array indices. In this case, i=p->x[a][b] will be turned into i=p->GetX(a, b), and p->x[a][b] = i will be turned into p->PutX(a, b, i);
Differential Revision: http://reviews.llvm.org/D13336

llvm-svn: 254067