This brings in the new ADC api for STM32 parts.
Update to new standardized ADC apis.
Drops pointless channel definitions, uses common names for common functions.
No functional changes.
Based on work in: https://github.com/libopencm3/libopencm3-examples/pull/130
Be specifically careful with the usb examples. There is likely some
breakage to be expected, not sure I updated all the drivers to the
correct types for the respective chips.
