Update res_fax and res_fax_spandsp to be compatible with Fax For Asterisk 1.2.

The fax session initilization code for T.38 faxes has been rewritten. T.38 session initialization was removed from generic_fax_exec, and split into two different code paths for receive and send.  Also the 'z' option (to send a T.38 reinvite if we do not receive one) was added to sendfax.

In the output of 'fax show sessions', the 'Type' column has been renamed to 'Tech' and replaced with a new 'Tech' column that will report 'G.711' or 'T.38'.

Control of ECM defaults has been added to res_fax

A 'fax show settings' CLI command has been added.

Support of the new AST_T38_REQUEST_PARMS control method request to handle channels that have already received a T.38 reinvite before the FAX application is start has been added.

Support for the 'fax show settings' command has been added to res_fax_spandsp and handling of the ECM flag has been slightly altered.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@258896 65c4cc65-6c06-0410-ace0-fbb531ad65f3