Summary: It turns out that perf_buffer API is only available in libbpf 0.2.0, which hasn't been released yet. To unblock katran, I grabbed the latest libbpf revision and created a temporary manifest. To avoid relying on this "beta" version libbpf on other projects only katran uses it. I'll make sure to remove it in favor of the official libbpf 0.2.0 once it's released.

Reviewed By: anakryiko

Differential Revision: D24156655

fbshipit-source-id: 32f6e04079a862fbfe96fd5475678cfa4ae1b3db