fhem.html: update warning added


git-svn-id: svn://svn.code.sf.net/p/fhem/code@5339 2b470e98-0d58-463d-a4d8-8e2adae1ed80
fhem.pl: AssignIoPort checks the IODev Attribute


git-svn-id: svn://svn.code.sf.net/p/fhem/code@5340 2b470e98-0d58-463d-a4d8-8e2adae1ed80
git-svn-id: svn://svn.code.sf.net/p/fhem/code@5341 2b470e98-0d58-463d-a4d8-8e2adae1ed80