Updating submodules
Updating submodules

Summary:
GitHub commits:

https://github.com/facebook/fbthrift/commit/c3798f17aa77bed8203a4a866d9bd950800c65f0
https://github.com/facebookexternal/stl_tasks/commit/c6e708b79db6f421f7398f0d57b2c53eeb271530
https://github.com/facebookincubator/velox/commit/195639a107b0c5ee512f933405b861466c51e879

Reviewed By: yns88

fbshipit-source-id: 74e6f65555aa0a5e832fa27e024b63c94983cbd9

facebook/bistro,facebook/bistro,facebook/bistro,facebook/bistro,facebook/bistro,facebook/bistro