Make wxList iterators conform to input iterator requirements

Define "pointer", "reference", "difference_type" and "iterator_category"
typedefs to ensure that wxList iterator classes are seen as iterators by
the standard library in C++11 and later, as otherwise standard container
template ctors taking iterators couldn't be used with them because
they're only available if input iterator requirements are satisfied.

This notably fixes creation of std::list from wxList iterators; add a
test which didn't compile before to show it.

tests/lists/lists.cpp

@@ -210,3 +210,27 @@ void ListsTestCase::wxListCtorTest()
     CPPUNIT_ASSERT( Baz::GetNumber() == 0 );
 }
 
+#if wxUSE_STD_CONTAINERS_COMPATIBLY
+
+#include <list>
+
+// Check that we convert wxList to std::list using the latter's ctor taking 2
+// iterators: this used to be broken in C++11 because wxList iterators didn't
+// fully implement input iterator requirements.
+TEST_CASE("wxList::iterator", "[list][std][iterator]")
+{
+    Baz baz1("one"),
+        baz2("two");
+
+    wxListBazs li;
+    li.push_back(&baz1);
+    li.push_back(&baz2);
+
+    std::list<Baz*> stdli(li.begin(), li.end());
+    CHECK( stdli.size() == 2 );
+
+    const wxListBazs cli;
+    CHECK( std::list<Baz*>(cli.begin(), cli.end()).empty() );
+}
+
+#endif // wxUSE_STD_CONTAINERS_COMPATIBLY