reverts #17656
we have to many xml nodes where this is allowed (e.g. command)
and limiting the linter to a statically defined list of node types
seemed difficult to maintain
replaced this with a change in the xsd that should lead to the
automatic removal of surplus white spaces (leading/trailing are removed,
multiple whitespaces are replaced by a single space) for some of the
node types that were the original motivation for the linter
(if this proves useful this could be used for more node types).
Matthias Bernt
c201daa7a8