condense case EV_REL: block into case EV_REL: case EV_ABS: block

Make the destinction between the two blocks a variable and combine the blocks.
remove *int_ptr variable
Merge branch 'feature/refrac-device-read' into develop
consolidate spacemouse_device_grab/_ungrab to spacemouse_device_set_grab
fix led event not being a seperate event in time

Reading evdev clients got an EV_LED, but is was directly prepended to
the next event without a seperate EV_SYN. The writing client are
responsable for sending this EV_SYN.
add struct and enum value for led events to headers
add led event support to spacemouse_device_read_event()

Use simpler type variable to keep track of what we already received and
add handling of EV_LED for led events.