Make sure the prompt works when autowrap is off

To reproduce the issue:

    $ echo -e '\E[?7l'

(cf. console_codes(4))

1 files changed, 5 insertions, 0 deletions

diff --git a/.bash_prompt b/.bash_prompt
index b42217f..b267dbc 100644
--- a/.bash_prompt
+++ b/.bash_prompt
@@ -170,6 +170,11 @@ __draw-rule ()
     do
         rule+=—
     done
+
+    # If we do not add a newline, the prompt will be shoved offscreen
+    # when autowrap is off.
+    rule+='\n'
+
     __fontify ${rule} dim
 }