Fix a few cppcheck findings
Merge pull request #1472 from LudwigOrtmann/cpp-check-a-bit

Fix a few cppcheck findings
native: uart reconnect buffer replay

When using socket stdio, add option to replay what has been written to
stdout while not connected (`-r`).

The implementation is to simply use the existing log file (which is
implicitly created when the option is used), and read from it until
EOF upon reconnect.

closes #476
native: cleanup

fix style
fix some syscall declarations
reorder syscall declarations
init syscalls in dedicated function
substitute 1 with EXIT_FAILURE
Merge pull request #1445 from LudwigOrtmann/issue-476

native: uart reconnect buffer replay (+a little cleanup)
cpu: atmega_common: Initial import
cpu: atmega2560: Initial import
board: arduino-mega2560: Initial import
tests: blacklist board arduino-mega2560:

    - tests/bloom: value too large for field of 2 bytes
    - tests/<other>: missing headers (time.h or sys/types.h)
test: add download of avr toolchain to .travis.yml
tests: blacklist tests/test_coap and examples that fail due to missing header files
boards: arduino-mega2560: cleanup of Makefiles
boards: arduino-mega2560: cleanup of periph_conf.h: remove left overs from
other board
boards: arduino-mega2560: fix indentation in errno.h
boards: arduino-mega2560: fix LED related defines
boards: arduino-mega2560: clean up LED init
cpu: atmega_common: move irq macros to irq_arch.c, fix indentation and doxgen
cpu: atmega2560: clean up Makefile
cpu: atmega2560: fix comment style
cpu: atmega2560: fix whitespace errors in header files and Makefile (periph)