rpl: mute RPL

Removes all but one occurrence of printf and puts within routing (the
remaining puts is called from a debug function.
add backspace functionality in shell
Add 0x7f as backspace key in shell
native: -DNATIVE_INCLUDES if using NATIVEINCLUDES

It can be useful to know if the current compilation builds the native
board module, because e.g. then we must not include `sys/types.h`.

This diff adds `-DNATIVE_INCLUDES` to the make variable
`NATIVEINCLUDES`.
 core: Provide ssize_t in a common place

 Now you can include `kernel_types.h` if you need the `ssize_t`, without
 facing problems due to the terrible MSP toolchain.
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
boards:mega2560: add debug and debug-server targets
Merge pull request #1696 from N8Fear/mega2560-debug

boards:mega2560: add debug and debug-server targets
drivers: import PIR motion sensor driver

Includes an application for manual testing.
Merge pull request #1714 from LudwigOrtmann/add_driver_pir

drivers: import PIR motion sensor driver
make: add objdump target
make: .PHONY missing targets from Makefile.include
Merge pull request #1723 from LudwigOrtmann/issue-1719

make: add objdump target + .PHONY missing targets from Makefile.include
Merge pull request #1698 from Kijewski/ssize_t-for-all

core: Provide ssize_t in a common place
pkg/Makefile.{http,git}: Minor issues resolved.

The were two recipes for clean. One of them is now "dist-clean"