Add documentation header for Folly::synchronize_rcu and Folly::rcu_barrier (#1306)
Add documentation header for Folly::synchronize_rcu and Folly::rcu_barrier (#1306)

Summary:
Pull Request resolved: https://github.com/facebook/folly/pull/1306

The current documentation for Folly::synchronize_rcu and Folly::rcu_barrier is lacking, this commit adds comment headers.

Reviewed By: magedm

Differential Revision: D18618910

fbshipit-source-id: 39e18d52b2380234ec6f33a1ec220acc97abdd50

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