Auto merge of #2612 - bsiegert:master, r=Amanieu
Auto merge of #2612 - bsiegert:master, r=Amanieu

NetBSD: add definition for execvpe

This is exactly the same as the OpenBSD definition. NetBSD has had
execvpe since the beginning, AFAICS.

rust-lang/libc,rust-lang/libc,rust-lang/libc