[xplat] Add Windows specific ATen build definitions (#40092)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40092
Move <windows.h> include in THAllocator after header that might include glog is included
Test Plan: buck build xplat/mode/arstudio/windows //xplat/caffe2:aten_cpuWindows
Reviewed By: nlutsenko
Differential Revision: D22061135
fbshipit-source-id: 10f51955c0092761a96bc6169236c6e07b412313
