[include/mCtrl/defs.h] Add inclusion of commctrl.h.

We will use some structure(s) from this header in our public interface.
Also (re)define some constants meant to be equivalent with constant from
that header to use their symbolic names.
[TREELIST] Add support for custom draw.
[TREELIST] Do not keep colors for each item.

It bloats the item structure and most apps do not use it.
When needed, app can use the custom draw API, which is actually more
powerful anyway.