Add ATmega2560 to cpu/avr/dev/clock-avr.h

Signed-off-by: chuljin <github@chuljin.com>
Merge branch 'master' of https://github.com/chuljin/contiki-arduino-propeller
cpu/avr/radio/rf230bb/rf230bb.c (rf230_transmit): extend comment on tx sequence

Explain that the transmission is intentionally started before copying the
frame to the buffer.
Merge branch 'master' of https://github.com/chuljin/contiki-arduino-propeller
Merge pull request #304 from frtos-wpan/rf230bb-merged

cpu/avr/radio/rf230bb/rf230bb.c (rf230_transmit): extend comment on tx s...
Update travis to use a newer SDCC

Due to SDCC bug #1986, we were previously stuck
with SDCC revision #7100. The bug was fixed with
rev #8719. Thus, we can now use newer versions

More info: http://sourceforge.net/p/sdcc/bugs/1986/
Merge pull request #319 from g-oikonomou/travis-new-sdcc

Update travis to use a newer SDCC
Switch to mspgcc 4.7.0
Updated mspsim.jar

The Contiki source code holds a binary version of mspsim.jar until
we get a proper git submodule set up. This particular version of mspsim.jar
is built from Thingsquare's mspsim fork.
Added mspgcc 4.7.x flags
Filter out symbols defined by the C implementation
Parse rodata too
Allow the exit code from a failed test script to propagate to the Java
process, which makes it possible to track failing tests in makefiles and
via scripts.
Turn off the LCD by default as it is somewhat flaky
Add CC2538 travis compile tests
Merge pull request #320 from g-oikonomou/travis-cc2538

Add CC2538 travis compile tests
Merge pull request #306 from adamdunkels/push/travis-mspgcc-4-7-0

Update travis to use mspgcc 4.7.0
Prevent erroneous index creation for non-numerical attributes.
Merge pull request #321 from nvt/antelope-domain-check

Prevent erroneous index creation for non-numerical attributes in Antelope.
Break travis compile tests into smaller builds

* The previous 01-compile test has been renamed to compile-base. It
  now only tests {msp430, avr, native}-based platforms
* New test builds for arm-based and 8051-based ports (one build per arch)
* Only install arm-none-eabi, sdcc and srecord for the builds which need
  them. This will somewhat speed up all other tests
* Test er-rest-example and webserver-ipv6 for the cc2538
* An erroneous comment was fixed and another comment was somewhat
  clarified