add example conf

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@6209 d0543943-73ff-0310-b7d9-9358b9ac24b2

conf/extensions.conf

+[default]
+exten => music,n,Dial(SIP/1234@conference.freeswitch.org|120)
+
+exten => _1XXXXX,n,set(cool=${EXTEN})
+exten => _1XXXXX,n,set(myvar=true)
+exten => _1XXXXX,n,Goto(default|music)
+