Fix VectorDistance initialization. (#1358)
Fix VectorDistance initialization. (#1358)

Summary:
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/1358

The MSVC compiler gets confused by aggregate initialization with parentheses.

Test Plan: Imported from OSS

Reviewed By: mdouze

Differential Revision: D23312003

Pulled By: beauby

fbshipit-source-id: 9ceb10ac84fd4aee19bf6352298b24def95f1493

facebookresearch/faiss,facebookresearch/faiss,facebookresearch/faiss,facebookresearch/faiss