fdo#38745: fix hilariously stupid stack guards:

The UndoRedoRedlineGuards that SwUndo::{Un,Re}doWithContext wants to
put on the stack aren't actually variables, so the destructor gets
invoked before the function call that the guard is supposed to protect.
Regression from CWS undoapi.

sw/source/core/undo/undobj.cxx

@@ -249,7 +249,7 @@ void SwUndo::UndoWithContext(SfxUndoContext & rContext)
             dynamic_cast< ::sw::UndoRedoContext * >(& rContext));
     OSL_ASSERT(pContext);
     if (!pContext) { return; }
-    UndoRedoRedlineGuard(*pContext, *this);
+    UndoRedoRedlineGuard const g(*pContext, *this);
     UndoImpl(*pContext);
 }
 
@@ -259,7 +259,7 @@ void SwUndo::RedoWithContext(SfxUndoContext & rContext)
             dynamic_cast< ::sw::UndoRedoContext * >(& rContext));
     OSL_ASSERT(pContext);
     if (!pContext) { return; }
-    UndoRedoRedlineGuard(*pContext, *this);
+    UndoRedoRedlineGuard const g(*pContext, *this);
     RedoImpl(*pContext);
 }