yum install autoconf automake make gcc-c++ 
yum install pcre-devel zlib-devel libmemcached-devel

wget https://github.com/downloads/libevent/libevent/libevent-2.0.21-stable.tar.gz
tar xfz libevent-2.0.21-stable.tar.gz
pushd libevent-2.0.21-stable
./configure
make
make install
popd

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:${PKG_CONFIG_PATH}

autoreconf -ivf

./configure --disable-tls

make 
make install