Uncommenting SO_PREFER_BUSY_POLL and SO_BUSY_POLL_BUDGET

[tammela]

I'm interested in these socket options which are commented out: https://docs.rs/libc/latest/src/libc/unix/linux_like/linux/arch/generic/mod.rs.html#109

Digging through the git history and issues I did not see any specific issue with these constants when they were added: https://github.com/rust-lang/libc/pull/2135

Is there any blocker for adding them?