Make mouse capture checking asserts stronger and more detailed.

Make mouse capture checking asserts stronger and more detailed.

Verify not only that we don't destroy the window having the capture now but
also that this window is not in the mouse capture stack at all, not
necessarily on top. This is important as keeping a dangling pointer in the
capture stack would result in difficult to diagnose bugs later.

Also check that we don't recapture the mouse in the same window as this should
never be necessary.

Finally, give more details in the assert checking that the window does have
capture in ReleaseMouse().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74677 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775