Add RELNOTES for 0.83.0rc2.
Add RELNOTES for 0.83.0rc2.

raboof/supybot,jeffmahoney/supybot,mazaclub/mazabot-core,Ban3/Limnoria,frumiousbandersnatch/supybot-code,kblin/supybot-gsoc,buildbot/supybot,mazaclub/mazabot-core,ProgVal/Limnoria-test,Ban3/Limnoria,prashantpawar/supybot-rothbot,haxwithaxe/supybot,ProgVal/Limnoria-test