Fix SIOF in torch using caffe2 registry (#16473)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16473
This resolves the issues associated with caffe2 initialization (specifically the REGISTER_FUNCTION_SCHEMA_OPERATOR calls) being run after Torch's static op registration calls.
The fix employs a meyer's singleton wrapped by the constructor of a type. Everything is placed inside a macro to make it easier for users to use.
Reviewed By: smessmer
Differential Revision: D13854306
fbshipit-source-id: ecf60861f229532826fae254974e9af4389055df
