Add an explicit option to replicate the whole computed liquid prompt in the window's title.
(Works with a vanilla xterm, but not under xterm-256 for me)
Add two color for the X11 support, green (support) and yellow (no support, not
set in red, because it is not a critical warning). The bold cyan of the hostname
was to close to the green of the colon and the @, change it to blue.
If the current connection supports X (if we are in a X session or if we have
enabled X11 forwarding under ssh), the @ displayed in front of the hostname
is colored in blue (use LP_COLOR_X11 to change the color).
