MT#57437 Upstream: increased libevent version

Backport from the upstream to support libevent-dev >= 2.1.12 .

Upstream commit: b2172dd70c2fe77c46e8427be5e3d0cf222cb049

Change-Id: Iea7e76b33c945cb57b8f2e98c9130ae46665c66c

debian/control

@@ -9,7 +9,7 @@ Build-Depends:
  flite-dev,
  libcurl4-openssl-dev | libcurl4-gnutls-dev,
  libev-dev,
- libevent-dev (>= 2.0.0),
+ libevent-dev (>= 2.1.12),
  libhiredis-dev,
  libmysql++-dev,
  libopus-dev,