doc: Refresh URLs in the qemu-tech documentation The TwoOStwo and Willows page seem to have disappeared completely, and also some of the other links were not pointing to the right locations anymore. Signed-off-by: Thomas Huth <thuth@redhat.com> Message-Id: <1443173916-8895-1-git-send-email-thuth@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>