Add missing include
Fixes build with libcxx, see also: https://bugs.gentoo.org/903575
The header replacing this one in upstream/master branch is peer.hpp
and it contains the missing include (commit 3952ff5c).
Fixes build with libcxx, see also: https://bugs.gentoo.org/903575
The header replacing this one in upstream/master branch is peer.hpp
and it contains the missing include (commit 3952ff5c).