Use wxIntNN types in wxQuantize code instead of INTNN ones.

Rely on the already properly defined wx types instead of using INTNN which
could clash with the system headers (e.g. INT32 is already defined in some
Motif headers) and are not guaranteed to be always defined correctly (while
int is always 32 bit on all currently supported platforms, this is not
guaranteed to always remain the case).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76745 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775