Update the URL of the web site images used in the test.

The old images don't exist any more after web site redesign.

Also, the new favicon can't be loaded from an unseekable stream because it
contains multiple icons, so point to the old favicon instead.

Closes #16049.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76088 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Document Insert() and Prepend() overloads taking wxMenu.

Document these methods in addition to AppendSubMenu().

Closes #16052.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76090 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775