stm32f0: be UART0 aware
stm32f4: be UART0 aware
stm32f3: be UART0 aware
stm32f1: unify UART0 use
stm32f*: rename STDIO buffer and enable getchar with UART0
Merge pull request #1471 from thomaseichinger/impl_uart0

cpu: make stm32f{0,1,3,4} comply to UART0 module
drivers: import PIR motion sensor driver
SQUASHME: remove missing GPIO workaround

Addresses https://github.com/RIOT-OS/RIOT/pull/1714#discussion_r18046571
SQUASHME: make private API static

Addresses https://github.com/RIOT-OS/RIOT/pull/1714#discussion_r18046365
SQUASHME: blacklist boards, provide defaults WIP
SQUASHME: add samr21-xpro define