Configure APB3 for appropriate clock sources during start-up.
Add GCC "used" attribute to prevent hard_fault_handler_c() from being removed. It trips up -flto.
Add parentheses to silence ambiguous expression warning.
Remove RF power enable from blinky -- it's not necessary.
Replace GPIO control of 1V8 supply with official function enable_1v8_power().
Add HackRF One RF power enable for samples that RX or TX.
USB0 and USB1 LEDs are only on Jellybean and Jawbreaker.
Do not configure BOOT[3:0] pins in SCU, as they should be idle/input/hi-Z on HackRF.
Merge pull request #121 from jboone/cleanup_201408

Miscellaneous clean-up