Fix the Folly OSS build by guarding the include of range-v3 header
Fix the Folly OSS build by guarding the include of range-v3 header

Summary: Folly OSS does not list range-v3 as a dependency. As a result, test/RangeTest.cpp fails to compile because it tries to include a range-v3 header. This change gates the inclusion of the header with `__has_include`, making the dependency optional.

Reviewed By: yfeldblum

Differential Revision: D20839733

fbshipit-source-id: 2d5e9c17427a0913f40f1ee80e868e27080a68f0

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