Add interface declarations to JIT (#21972)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21972
ghimport-source-id: 280f89ca678615f915be2139d1c05cb6bc39eefc
Test Plan: Imported from OSS
Differential Revision: D15901930
Pulled By: zdevito
fbshipit-source-id: 22c82d12c9c2600e569d7083e2771fd6ec3de2b1
