HAS_FEATURE fix
HAS_FEATURE fix

Summary: Foolishly #defined __has_feature when it wasn't and let it leak, but something later must have been relying on something similar. This replaces the uses with FOLLY_HAS_FEATURE.

Reviewed By: yfeldblum, magedm

Differential Revision: D6829724

fbshipit-source-id: 40635dd67135316f27be2aa2a6b2d579dbf843e1

facebook/folly,facebook/folly,rklabs/folly,facebook/folly,facebook/folly,rklabs/folly,facebook/folly,rklabs/folly,rklabs/folly,rklabs/folly