doc: fix comment indentation
doc: use lgplv2.1-short license header instead of lgpl-short-riot
doc: use lgplv2.1-short license header instead of lgplv2-short-v3
doc: use lgplv2.1-short license header instead of lgplv2-short-v2
doc: use lgplv2.1-short license header instead of lgplv2-short-v1
Merge pull request #1329 from LudwigOrtmann/riot_license

RIOT default license header change