Merge remote-tracking branch 'upstream/master'
Bumped the version number from 2.6 to 3.x, which is to be used in the development branch
Have CBM DOS filetype of imported files match the one used by cc65.

CFS_WRITE implies O_TRUNC which is implemented on CBM DOS by deleting an
exsisting file. Hoewever this succeeds only if the CBM DOS filetype matches.

We need a working O_TRUNC in order to be able to overwrite the contiki.cfg
configuration file.

Note: Now it has be clarified why overwriting the configuration file started to
fail the CBM PFS (platform file system) can be activated for the recently added
ethconfig program.
Merge remote-tracking branch 'upstream/master'
Moved #defines so that UIP_TCPIP_HLEN and UIP_LLH_LEN are defined before they are used
Make 0 the default link-layer header length, as far as uIP is concerned. Most currently used linke layers (specifically, 802.15.4) has adaptation layers that use separate buffers, so there is no need to reserve space in the uIP buffer.
Removed redundant #ifdef
Fixed a severe error in the bugfix: the conditional was reversed. The check must be if the TCP MSS is larger than the BUFSIZE and not the other way around.
Merge pull request #501 from oliverschmidt/master

Have CBM DOS filetype of imported files match the one used by cc65.
Merge pull request #498 from adamdunkels/push/contiki-3.x

Bump the version number in the development branch
Merge pull request #502 from adamdunkels/push/fix-the-ipv6-bugfix

Fix the IPv6 bugfix
Cooja/DGRM: Allow setting the RSSI value when sending or during silence.
concurrency fix set/get BaseRssi
Fixed the concurrency of the WeakHashMap used by setBaseRssi and getBaseRssi and running the updateSignalStrengths in a Simulation Thread because of concurrency
BaseRSSI plugin added
plugin to view and change the base rssi.
for further implementation of random base rssi generation
BaseRSSI for all RadioMediums - just MRM not working
SendRSSI also moved to AbstractRadioMedium
get/setConfigXML added