Fix XFailed test x86stdcall

There was a syntax error because the `extern "stdcall"` was outside the module instead of inside it.

* moved `extern` inside module
* updated copyright dates
* change `cfg(target_os="win32")` to `cfg(windows)`
* change `extern "stdcall"` to `extern "system"`
* only run on Windows && x86, (not x86_64)
auto merge of #10363 : astrieanna/rust/fix-x86stdcall, r=alexcrichton

* moved `extern` inside module
* changed `extern "stdcall"` to `extern "system"`
* changed `cfg(target_os="win32")` to `cfg(windows)`
* only run on Windows && x86, (not x86_64)
* updated copyright dates