tools: record: record the EV_ABS deltas along with the absolute value

tools: record: record the EV_ABS deltas along with the absolute value

It's useful to have this in the immediate recording. Example output now:

 - evdev:
    - [  2, 300309,   3,  47,       0] # EV_ABS / ABS_MT_SLOT               0
    - [  2, 300309,   3,  54,    3547] # EV_ABS / ABS_MT_POSITION_Y      3547 (+8)
    - [  2, 300309,   3,  58,      70] # EV_ABS / ABS_MT_PRESSURE          70 (-14)
    - [  2, 300309,   3,  47,       1] # EV_ABS / ABS_MT_SLOT               1
    - [  2, 300309,   3,  54,    3112] # EV_ABS / ABS_MT_POSITION_Y      3112 (+4)
    - [  2, 300309,   3,  58,      68] # EV_ABS / ABS_MT_PRESSURE          68 (-4)
    - [  2, 300309,   3,   1,    3547] # EV_ABS / ABS_Y                  3547 (+8)
    - [  2, 300309,   3,  24,      70] # EV_ABS / ABS_PRESSURE             70 (-14)
    - [  2, 300309,   0,   0,       0] # ------------ SYN_REPORT (0) ---------- +49ms

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>