Changing git submodule libopencm3 to arcoslab repo.
Switched libopencm3 to stm32f3 branch.
stm32f3discovery examples added.

- miniblink
- button
- fancyblink
- adc
- Non tested yet! But they compile.
stm32f3discovery ld script corrected as recommended in #82. libopencm3 updated.
Flashing now using openocd. GDB Debugging possible and tested :).
libopencm3 updated to lastest stm32f3 commit.
Adc example fixed (printing garbage before) and cleaned.

- Integer printing function fixed.
  	  - because of comparison against smaller than 0 numbers we must use signed numbers!
	  - Value zero was not printed at all.
	  - It was printing one more character than it should.
- Erasing unnecesary commentaries.
- Erasing debugging help.