Implement MBOX callback function for PLASMA Cutter
Implement MBOX callback function for PLASMA Cutter

* MBOX callback function name: fetchmail()
* MAIL_TAG for PLASMA is 0x0001
* Add "analog input" to "gpio" data structure

araisrobo/linuxcnc,araisrobo/linuxcnc,araisrobo/linuxcnc,araisrobo/linuxcnc,araisrobo/linuxcnc