lib: Generate pkgconfig file

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
.git: add cgroup01 to gitignore

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
lib: return -ECONNREFUSED as documented

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
build: install target depends on libcriu

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
lib: Initialize child messages correctly

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>