Update libopencm3 and example for STM32F0

This is a simple STM32F0DISCOVERY example using the systick interrupt. 

The reference to libopencm3 needs to be updated because the older revision does not seem to include STM32F0 support. Note that I changed the file examples/stm32/f1/stm32-h103/traceswo/traceswo.c and these changes need a review.