Clean up Half (#15317)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15317
- Merge bitcasts.h and Half.h
- Remove 'static' keyword
Reviewed By: dzhulgakov
Differential Revision: D13498492
fbshipit-source-id: 46d47143e7d3a9d3f4aa7d92379dbba015c97435
