===== ERROR while installing zmq.4.0-3 =====
# opam-version 1.1.1
# os           linux
# command      ocaml setup.ml -build
# path         /home/xx/.opam/4.01.0/build/zmq.4.0-3
# compiler     4.01.0
# exit-code    1
# env-file     /home/xx/.opam/4.01.0/build/zmq.4.0-3/zmq-6378-5f1023.env
# stdout-file  /home/xx/.opam/4.01.0/build/zmq.4.0-3/zmq-6378-5f1023.out
# stderr-file  /home/xx/.opam/4.01.0/build/zmq.4.0-3/zmq-6378-5f1023.err
### stdout ###
# ...[truncated]
# pkg_str: ............................................. /home/xx/.opam/4.01.0/lib/ocaml
#
# /home/xx/.opam/4.01.0/bin/ocamlopt.opt unix.cmxa -I /home/xx/.opam/4.01.0/lib/ocaml/ocamlbuild /home/xx/.opam4.01.0/lib/ocaml/ocamlbuild/ocamlbuildlib.cmxa myocamlbuild.ml /home/xx/.opam/4.01.0/lib/ocaml/ocamlbuild/ocamlbuild.cmx -o myocamlbuild
# ocamlfind ocamlc -ccopt -I -ccopt '${pkg_uint_uint64}' -ccopt -Wall -ccopt -Wextra -ccopt -O2 -c src/caml_zmq_stubs.c
# + ocamlfind ocamlc -ccopt -I -ccopt '${pkg_uint_uint64}' -ccopt -Wall -ccopt -Wextra -ccopt -O2 -c src/caml_zmq_stubs.c
# src/caml_zmq_stubs.c:37:20: fatal error: uint64.h: No such file or directory
#  #include <uint64.h>
#                     ^
# compilation terminated.
# Command exited with code 2.
### stderr ###
# E: Failure("Command ''/home/xx/.opam/4.01.0/bin/ocamlbuild' src/libZMQ_stubs.a src/dllZMQ_stubs.so src/ZMQ.cma src/ZMQ.cmxa src/ZMQ.a src/ZMQ.cmxs examples/hwserver.native examples/hwclient.native examples/wuserver.native examples/wuclient.native examples/wuproxy.native examples/taskvent.native examples/taskwork.native examples/tasksink.native -tag debug' terminated with error code ...[truncated]

'opam install zmq' failed.