Include <cassert> when using assert
Include <cassert> when using assert

Summary:
We were using `assert` without including anything that defines it.

Closes https://github.com/facebook/folly/issues/530

Reviewed By: yfeldblum

Differential Revision: D4337047

fbshipit-source-id: 327d19a685e7a4cc1e1eb6e471a6457fe9dee6c7

facebook/folly,rklabs/folly,Orvid/folly,rklabs/folly,rklabs/folly,Orvid/folly,Orvid/folly,charsyam/folly,charsyam/folly,floxard/folly,Orvid/folly,facebook/folly,facebook/folly,rklabs/folly,floxard/folly,charsyam/folly,facebook/folly,facebook/folly,charsyam/folly,floxard/folly,rklabs/folly,Orvid/folly,floxard/folly,floxard/folly