With this a TS-I tip is usable with a small netbook 19 V / 30 W PSU with
power limit set to 40 W (38.9 W is reported during the heating up
stage). Without this the device just reboots on attempt to turn on the
heater (unless the power limit is set to 10 or even 5 W).
This code doesn't affect maximum power available and allows up to 73 W
when a beefy 24 V / 96 W PSU is used.
Should be useful for all models, not just TS100.
The fixed comments are based on calculations, not measurements!
Fixes#693.
