- add comment on null, xp::null - add comment on $callToString parameter
- add comment on null, xp::null
- add comment on $callToString parameter

git-svn-id: 526f3b90ad6d9b1dfe840af828070ca3d99521ac@6605 d2cacbed-c0f6-0310-851a-9dad52fc623a

johannes85/core