Update libevent to 2.1.11 Use CMake instead GNU Autotools Backport following commits:f05ba67193..and partially7201062f3eto fix compilation Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net> (cherry picked from commitf351beedfd) (resolves FS#2435) Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>