support malloc wrapping on Windows 8

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on October 28, 2013 12:57:52_

I thought there was an issue on this but I can't find it.
Xref issue #772 .
There were enough unaddrs and other false positives showing up from the heap layers on Win8 (had problems with our tests with /MDd, /MTd, or /MT, and I recall deeper issues in Rtl layers?) that I switched to -replace_malloc to solve them all. However, we want to keep supporting wrapping for Dr. Malloc for better transparency for tools that want to analyze an app's unperturbed memory behavior (e.g., profiling tools, or security tools). Xref issue #1358 .

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1359_