Disown ssh+git and git+ssh

Disown ssh+git and git+ssh

Some people argue that these were silly from the beginning (see
http://thread.gmane.org/gmane.comp.version-control.git/285590/focus=285601
for example), but we have to support them for compatibility.

That doesn't mean we have to show them in the documentation.  These
were already left out of the main list, but a reference in the main
manpage was left, so remove that.

Also add a note to discourage their use if anybody goes looking for them
in the source code.

Signed-off-by: Carlos Martín Nieto <cmn@dwim.me>
Signed-off-by: Junio C Hamano <gitster@pobox.com>