Clean up my TODO comments in SmallMap and Time.
The TODO in time.h was about removing time_t functions. When I wrote this I was optimistically thinking we wouldn't use time_t any more now that we have the awesome new Time class. This was fantasy so the TODO is removed.
SmallMap uses ManualConstructor. The TODO was that these could be removed when we have C++11 unions. This is true, but the syntax looked worse. There was a use in ConvertToRealMap that still required ManualConstructor for optimum allocations, so it seemed best to just keep using ManualConstructor.
However, the necessity of having the dummy value in the union due to an MSVC error seems no longer applicable. The dummy value is removed.