Fix incorrect interpretation of arm condition codes (affects single stepping).
Note that case 13 (LE) must be the converse of case 12 (GT).
Perhaps not coincidentally, the same mistake appears in my paper copy of the
ARM architecture reference manual (1996 ed).

Reference: /n/sources/patch/applied/5db-condcode
Date: Fri Aug  2 22:22:17 CES 2013
Signed-off-by: miller@hamnavoe.com

--- /sys/src/libmach/5db.c	Fri Aug  2 22:16:10 2013
+++ /sys/src/libmach/5db.c	Fri Aug  2 22:16:05 2013
@@ -601,7 +601,7 @@
 	case 10:	return n == v;
 	case 11:	return n != v;
 	case 12:	return !z && (n == v);
-	case 13:	return z && (n != v);
+	case 13:	return z || (n != v);
 	case 14:	return 1;
 	case 15:	return 0;
 	}