declare the postal service iterators as values, not as references

PostalService.h names every type twice, once plainly and once as a reference:
RefToDestinationStruct is DestinationStruct&, RefToShipmentList is
ShipmentList&. That scheme was extended to the iterators, and there it does
not work. Every one of the seventeen uses looks like this:

    RefToShipmentListIterator sli = _Shipments.begin();

begin() returns a value, so this binds a non-const reference to a temporary.
MSVC allows it as an extension; the temporary still dies at the end of the
full expression, which leaves sli referring to a dead object for the whole
rest of the function. It works only because nothing has reused the stack slot
yet. clang rejects it outright.

Iterators are already handles into their container, so a reference to one buys
nothing: the plain typedef says exactly what these seventeen variables want to
be. DESTINATION and SHIPMENT now take theirs by value, which changes nothing
for either, as both only dereference the iterator they are given.

Two of the reference typedefs, RefToDestinationDeliveryInfoTableIterator and
RefToDeliveryCallbackDataListIterator, had no uses at all. They are removed
rather than left behind, since their only possible use is the pattern this
commit removes.

Verification:

    grep -rn 'RefTo[A-Za-z]*Iterator' --include=*.cpp --include=*.h .   # nothing
    ninja -C build parse         # bind-to-temporary class gone: 91 -> 60 sites
    ninja -C build -k 0          # Release, four applications, green
    ninja -C build-debug -k 0    # Debug, four applications, green

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Laptop/XML_DeliveryMethods.cpp

@@ -23,7 +23,6 @@ typedef DestinationDeliveryInfoReadInStruct& RefToDestinationDeliveryInfoReadInS
 typedef vector<DestinationDeliveryInfoReadInStruct> DestinationDeliveryInfoReadInTable;
 typedef DestinationDeliveryInfoReadInTable& RefToDestinationDeliveryInfoReadInTable;
 typedef DestinationDeliveryInfoReadInTable::iterator DestinationDeliveryInfoReadInTableIterator;
-typedef DestinationDeliveryInfoReadInTableIterator& RefToDestinationDeliveryInfoReadInTableIterator;
 
 enum
 {
@@ -145,7 +144,7 @@ deliveryMethodEndElementHandle(void *userData, const XML_Char *name)
 			pData->curElement = DELIVERYMETHOD_ELEMENT_TABLE;
 			UINT8 ubCurrentDM = gPostalService.AddDeliveryMethod(pData->CurDeliveryMethod.szDescription);
 			
-			RefToDestinationDeliveryInfoReadInTableIterator dfriti = pData->CurDeliveryMethod.DestinationDeliveryInfos->begin();
+			DestinationDeliveryInfoReadInTableIterator dfriti = pData->CurDeliveryMethod.DestinationDeliveryInfos->begin();
 
 			while(dfriti != pData->CurDeliveryMethod.DestinationDeliveryInfos->end())
 			{