IDE: build modes: error message when duplicate name

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41496 4005530d-fff6-0310-9dd1-cebe43e6787f
IDE: replaced some MessageDlg with IDEMessageDialog

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41497 4005530d-fff6-0310-9dd1-cebe43e6787f