Minor documentation corrections.

Escape the space after "i.e." (or avoid using it altogether), add missing @ref.

Closes #16235.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76472 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Allow using sizers for laying out wxMDIClientWindow in wxMSW.

Let the user code put wxMDIParentFrame::GetClientWindow() into a sizer and
manage it as any other window, instead of having to do it manually.

Closes #16196.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76473 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775