FPDebug: scan all units

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43394 4005530d-fff6-0310-9dd1-cebe43e6787f
LazUtils: allow ReleaseRef on nil

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43395 4005530d-fff6-0310-9dd1-cebe43e6787f