Bug 660730: Win32: Only use _fstat32 if available

Bug 660730: Win32: Only use _fstat32 if available

_fstat32 is only introduced with msvcrt80.dll (i.e. Visual C++ 2005), in
which using this function will break compilation with MinGW, which links
against msvcrt.dll.  The msvcrt.lib in the Windows DDK which links to
a later incarnation of the msvcrt.dll in later Windows systems may have
this symbol defined, but that needs to be checked upon to be sure.

Thanks to Dieter Verfaillie for pointing out this problem.