* added possibility to change echocancel settings during calls

* added possibility to change echocancel settings during calls
* removed the holded element from the chan_list struct, we know this from the
  state already
* added a few tweaks to make HOLD/RETRIEVE work again (TRANSFER does not work
  yet)
* added possibility to debug mISDN frames via syslog
* added misdn_lib_port_is_blocked function to check if a port is blocked
* removed ec_training=1 from empty_bc, we don't use ec_training anymore
* removed unused misdn_lib_get_l2_status function
* added the nt bit to dummy misdn_bchannel objects
* setting bc->out_fac_type to FACILITY_NONE defaultly
* removed HANDLER_DEBUG stuff for better readability

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@39295 65c4cc65-6c06-0410-ace0-fbb531ad65f3