Fix pointer truncation in wxListEvent::GetData() in LLP64 builds.

We must use wxUIntPtr and not long here to avoid truncating the upper half of
the pointer when sizeof(void*)>sizeof(long).

Closes #15578.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75005 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -568,6 +568,10 @@ All:
 - Add possibility to validate the input files against a schema to wxrc.
 - Fix recently broken compilation with Intel compiler.
 
+All (GUI):
+
+- Fix wxListEvent::GetData() in LLP64 builds.
+
 wxMSW:
 
 - Optional better handling of SAFEARRAYs in wxAutomationObject (PB).