XLIFF: Set xml:space="preserve" for entries created using ITS rule with itsx:whiteSpaces="preserve"

Created by: Anonymous

Original issue 311 created by khagar... on 2013-02-03T08:42:36.000Z:

When configuring custom ITS with entries using itsx:whiteSpaces="preserve", the extracted entries in XLIFF do have the spaces preserved, but don't have xml:space="preserve" set, so processing them in tools that do not treat XLIFF as xml:space="preserve" by default (fe. OmegaT) results in wrong translations. If the entry is created by a ITS rule with itsx:whiteSpaces="preserve" it should have xml:space="preserve" set.