Add a wxFTP::Connect() overload taking a port number.
Also specify the default port (21) explicitly if resolving "ftp" service name
failed.
Closes#12145.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64621 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775