Escape new line characters in xml strings. (#9512)

  - Our xml parser (expat) does not seem to parse newlines in xml attributes.
    So change
      - all new lines `(\n)` to their xml value `
`
      - all carrage returns `(\r)` to their xml value `
`

    before writing them to the xml files.

    It might be some settting we have to set for expat. Maybe someone who
    knows expat can suggest an alternative.

  - Fixes #9429.

OMCompiler/Compiler/Util/Util.mo

@@ -919,6 +919,8 @@ algorithm
   xmlString := System.stringReplace(xmlString, "\"", """);
   xmlString := System.stringReplace(xmlString, "<", "&lt;");
   xmlString := System.stringReplace(xmlString, ">", "&gt;");
+  xmlString := System.stringReplace(xmlString, "\n", "&#10;");
+  xmlString := System.stringReplace(xmlString, "\r", "&#13;");
   // TODO! FIXME!, we have issues with accented chars in comments
   // that end up in the Model_init.xml file and makes it not well
   // formed but the line below does not work if the xmlString is