Fix so the Host: header in wxHTTP really works. With virtual hosts it

Fix so the Host: header in wxHTTP really works.  With virtual hosts it
is vital that the original host name given in the URL is used in the
Host: header so the sever will use the right vhost config.  Previously
it was using the value returned from gethostbyaddr which will often
not be the same as the hostname in the URL.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14332 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775