LCL: gtk2: check if gtk_window

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40262 4005530d-fff6-0310-9dd1-cebe43e6787f
lazutils: disabled workaround for fpc 2.7.1

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40263 4005530d-fff6-0310-9dd1-cebe43e6787f
lazutils: disabled workaround for fpc 2.7.1

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40264 4005530d-fff6-0310-9dd1-cebe43e6787f
LCL: comments

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40265 4005530d-fff6-0310-9dd1-cebe43e6787f