added support for pure REL/ABS devices (such as rotary encoders)

[trurle]

some input devices such as rotary encoders don't have keys or switches, but can generate EV_REL/EV_ABS events. this simple change allows these devices to be used with triggerhappy. I checked with my two rotary encoders and it works. thanks!

[melsem]

I join.
Make changes.
Hurrah..
I checked encoder, works!
Thank trurle!

/dev/input/event3 - rotary encoders

root@orangepi-zero:~# evtest
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:	gpio-keys-user
/dev/input/event1:	rotary_button
/dev/input/event2:	sunxi-ir
/dev/input/event3:	rotary_axis
/dev/input/event4:	HID 0513:0318
/dev/input/event5:	HID 0513:0318
Select the device event number [0-5]: 3
Input driver version is 1.0.1
Input device ID: bus 0x19 vendor 0x0 product 0x0 version 0x0
Input device name: "rotary_axis"
Supported events:
  Event type 0 (EV_SYN)
  Event type 2 (EV_REL)
    Event code 1 (REL_Y)
Properties:
Testing ... (interrupt to exit)
Event: time 1614505570.405308, type 2 (EV_REL), code 1 (REL_Y), value 1
Event: time 1614505570.405308, -------------- SYN_REPORT ------------
Event: time 1614505571.370003, type 2 (EV_REL), code 1 (REL_Y), value 1
Event: time 1614505571.370003, -------------- SYN_REPORT ------------
Event: time 1614505572.359239, type 2 (EV_REL), code 1 (REL_Y), value -1
Event: time 1614505572.359239, -------------- SYN_REPORT ------------
Event: time 1614505573.284278, type 2 (EV_REL), code 1 (REL_Y), value -1
Event: time 1614505573.284278, -------------- SYN_REPORT ------------
root@orangepi-zero:~#
root@orangepi-zero:~#
root@orangepi-zero:~# thd --dump /dev/input/event*
EV_REL	REL_Y	-1	/dev/input/event3
# REL_Y	-1	command
EV_REL	REL_Y	-1	/dev/input/event3
# REL_Y	-1	command
EV_REL	REL_Y	1	/dev/input/event3
# REL_Y	1	command
EV_REL	REL_Y	1	/dev/input/event3
# REL_Y	1	command
root@orangepi-zero:~#