This avoids out of order deallocation issues

replace with glibc %m in format strings

Now AudioZrtpSession and AudioSymmetricRtpSession are derived from it, and AudioSrtpSession is derived from AudioSymmetricRtpSession
AudioRtpSession class keeps a pointer to the RTPDataQueue and Thread casts of the 2 specialized classes to access a few, because AudioRtpSession doesn't derive from RTPDataQueue or Thread directly.

(cherry picked from commit c3081dce)

It would only hide the password for the first entry, and was buggy:
The real password would be overwritten by the masking entry (*****)

We need to find something else

The SIP credentials are transmitted (between client and daemon) and
(un)serialized (in the config file) as a list of items holding:
    - realm
    - username
    - password

The password associated to the SIP account will be removed as it is
redundant with the first item of the list.
idem for the authentication username.

Do not remove the call from internal list
It will not be displayed, and will be removed from the list when receiving the success reponse for the transfer

So move accountID from SIPVoIPLink to IAXVoIPLink

It is set by the constructor
No need to unserialize it again either