Update libevent to 2.1.11
Use CMake instead GNU Autotools
Backport following commits:
f05ba67193
..and partially
7201062f3e
to fix compilation
Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>
(cherry picked from commit f351beedfd)
(resolves FS#2435)
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
