Gigabeat S: Add charge current and battery temp readout in power management and displ...

Gigabeat S: Add charge current and battery temp readout in power management and display in the battery screen. Thermistor data was obtained experimentally from one pulled off a dead board and appears basically correct when read back on a working device (which requires letting it settle to ambient temperature - a long wait so not easy to do). Sending me more thermistors would help improve accuracy *fingers crossed that it's close enough*. :-) This commit does NOT add charging but is a step towards implementing it.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17626 a1c6a512-1295-4272-9138-f99709370657