History -b didn't work as documented.

Notes:
Mon Apr 16 13:19:24 EDT 2007 geoff
    Declined; the code is correct, the manual page was unclear.
    I've fixed the manual page.


Reference: /n/sources/patch/sorry/history-diffnb
Date: Sat Apr 14 18:36:14 CES 2007
Signed-off-by: m.ne@gmx.net
Reviewed-by: geoff

--- /sys/src/cmd/history.c	Sat Apr 14 18:09:16 2007
+++ /sys/src/cmd/history.c	Sat Apr 14 18:09:13 2007
@@ -41,6 +41,7 @@
 		diff = 1;
 		break;
 	case 'b':
+		diff = 1;
 		diffb = 1;
 		break;
 	case 's':