Windows wants ISO C++ _fileno and _unlink instead of posix fileno and
unlink. For fileno we have the QT_FILENO macro in qplatformdefs.h, so use
it. For unlink we don't have a macro in Qt, so declare one in the test.
Change-Id: I56c5c3fb4e500769c744132c46107816f89bb2c3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>