RIOT-OS/RIOT — pull request #2191 by cgundogan (2014-12-14 10:25:31+00:00)
Title: rpl:remove send mutex

This PR is *based* on #2155.
Since RPL/Trickle is only using one thread in #2155, the send mutex becomes
obsolete and can be removed safely.

**The diff seems quite large, because it also compares the changes made in #2155 with master.**