starmath: directly create utf8 OUString

This fixes:

warn:rtl.string:14867:1:sal/rtl/strtmpl.cxx:1269: rtl_uString_newFromLiteral - Found char > 127

Change-Id: I1f868406501c83918fc3c06dd0b68eb1f6604f26

starmath/source/ElementsDockingWindow.cxx

@@ -481,7 +481,7 @@ void SmElementsControl::addElements(const sal_uInt16 aElementsArray[][2], sal_uI
             addSeparator();
         } else {
             if (aElementId == RID_NEWLINE)
-                addElement(OStringToOUString( "\xe2\x86\xb5", RTL_TEXTENCODING_UTF8 ), SM_RESSTR(aElementId), SM_RESSTR(aElementIdHelp));
+                addElement(OUString( "\xe2\x86\xb5", 3, RTL_TEXTENCODING_UTF8 ), SM_RESSTR(aElementId), SM_RESSTR(aElementIdHelp));
             else if (aElementId == RID_SBLANK)
                 addElement("\"`\"", SM_RESSTR(aElementId), SM_RESSTR(aElementIdHelp));
             else if (aElementId == RID_BLANK)