Added control of remote RXes via Voter using a PTY (VOTER_PTY).

[hsmade]

Just echo into the VOTER_PTY: :0 to disable or :1 to enable.
This will mute the RX and set its status to disabled so it won't be selected by the voter anymore.
On enable, it becomes available for selection and the mute is set to none.
Also prints status on STATE_PTY (Voter:opr_state rx1:0 rx2:1) so it can be picked up by the perl script, for example.

[pe1chl]

I think it is a great idea and a first start for the implementation of the enhancement described in issue #136.
However, I think it would be better to make a general PTY for sending commands to SvxLink and then interpret the commands and forward them to the proper part of SvxLink.
I.e. one can send commands like:

DTMF 123455   (the same that is already available on stdin when not running as daemon)
RxEnable rxname:1  (the thing that was added by this modification)

etc, and it can be extended with new commands when the need arises without having to create more and more PTYs.

[hsmade]

I agree that this would be the correct solution. However, it's not that easy because the other PTY is handled by a different object which has no knowledge of the voter in that sense (as far as I could see). That's why I made it a separate PTY as a POC. I hope someone can take this code is a start to get it to the correct level.

I like your idea of sending DTMF through the PTY as well. This could be a start of better runtime administration and manipulation of svxlink.