respect banner argument in TerminalInteractiveShell.interact

banner was interpreted as boolean arg, rather than accepting a string,
so specifying shell.interact(msg) will actually set the banner, as it should.

IPython/frontend/terminal/interactiveshell.py

@@ -238,7 +238,10 b' class TerminalInteractiveShell(InteractiveShell):'
 
         if display_banner is None:
             display_banner = self.display_banner
-        if display_banner:
+        
+        if isinstance(display_banner, basestring):
+            self.show_banner(display_banner)
+        elif display_banner:
             self.show_banner()
 
         more = False