IDE: mode matrix: update if in session changed

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41495 4005530d-fff6-0310-9dd1-cebe43e6787f
IDE: build modes: error message when duplicate name

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41496 4005530d-fff6-0310-9dd1-cebe43e6787f