into a usable function - this has some coding style issues I did not care to
fix.
* _AddBaseMode() now computes the mode in case it is not present in the list
yet.
* This should help with bug #7787.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42420 a95241bf-73f2-0310-859d-f6bbb57e9c96