按照官方安装文档安装会报错，原因是官方的文档在安装pjsip的时候版本较低，改下版本即可
官方是 wget http://www.pjsip.org/release/2.4/pjproject-2.4.tar.bz2，
改成一下wget http://www.pjsip.org/release/2.8/pjproject-2.8.tar.bz2
https://wiki.freepbx.org/display/FOP/Installing+FreePBX+13+on+CentOS+7
https://wiki.freepbx.org/display/FOP/Installing+FreePBX+14+on+CentOS+7