Use "int" instead of "long" for TLW geometry storage

For some reason, "long" was used for window coordinates even though they're
really "int", and implicitly converting from the former to the latter resulted
in warnings in user code including this header with e.g. Apple clang.

Just use int to avoid conversions.

include/wx/persist/toplevel.h

@@ -79,7 +79,7 @@ public:
     {
         wxTopLevelWindow * const tlw = Get();
 
-        long x wxDUMMY_INITIALIZE(-1),
+        int x wxDUMMY_INITIALIZE(-1),
             y wxDUMMY_INITIALIZE(-1),
             w wxDUMMY_INITIALIZE(-1),
             h wxDUMMY_INITIALIZE(-1);