[racket] Handle variant VT_DATE

At Tue, 16 Apr 2013 11:53:59 +0200 (CEST), "murat demirtas" wrote:
> how can I handle  VT_DATE as return value in ffi/com scripting
>  
> I get an error like this: 
> VariantTimeToSystemTime: implementation not found; arguments: 41353.5534375 
> #<cpointer:SYSTEMTIME>

Unfortunately, there are several problems with using date values. The
most immediate problem is that `ffi/com' attempts to find
VariantTimeToSystemTime() in "ole32.dll" instead of "oleaut32.dll";
another problem is that the return value is treated backwards.

I've pushed repairs to the git repo, and the repairs will be included
in the upcoming v5.3.4 release.