Core/Gossip: Change max menu items to 32

Tested and a gossip menu can show max 32 items on a menu.
When sending 40 options: http://puu.sh/7rqb6.jpg
Merge pull request #11694 from Rochet2/patch-1

Core/Gossip: Change max menu items to 32
Merge remote-tracking branch 'trinitycore/master'