Fix documentation for lifo.h
Fix documentation for lpm.h
Fix documentation for msg.h
Fix documentation for mutex.h
license: %s/FeuerWare/RIOT/g
Merge pull request #1147 from LudwigOrtmann/riotisnotfeuerware

license: %s/FeuerWare/RIOT/g
Merge pull request #962 from authmillenon/issue-953

core: doc: documentation improvement lifo.h lpm.h msg.h mutex.h
sys: add utility functions for `struct tm`
Add `struct tm` utility "test"