GPIO not unbound after closing.

[j-gallardo]

Hi,I'm using GPIO to control PTT. I have found that the gpio port is not released when rigclt/rigctld is closed. I'm using a sbc Nextthingco C.H.I.P., with the following configuration:
Linux chip 4.4.13-ntc-mlc #1 SMP Tue Dec 6 21:38:00 UTC 2016 armv7l GNU/Linux
Debian 8 (jessie), variant "Debian no C.H.I.P."
gcc (Debian 4.9.2-10+deb8u2) 4.9.2

To control my Icom IC706 I use:
#rigctl -m 3009 -c 0x48 -r /dev/ttyS0 -s 19200 -P GPIO -p 1013
where 1013 is the gpio port number.
It works perfectly the first time, but if I close rigctl and open it again, it won't communicate with the rig. The solution is to unbind the port with: 
#sh -c 'echo 1013 > /sys/class/gpio/unexport'
I suggest this should be included in the gpio_close function.
I'm not a real developer, so it will take long until I fix it in the code. If I get it done I will submit the solution to github.
Thanks for the hard work.