document -S, 2-byte swizzle

Reference: /n/atom/patch/applied2013/xdman
Date: Tue Jun 18 20:13:24 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/man/1/xd	Tue Jun 18 20:13:13 2013
+++ /sys/man/1/xd	Tue Jun 18 20:13:13 2013
@@ -75,6 +75,8 @@
 .B -s
 Reverse (swab) the order of bytes in each group of 4 before printing.
 .TP
+.B -S
+Reverse (swab) the order of bytes in each group of 2 before printing.
 .B -r
 Print repeating groups of identical 16-byte sequences as the first group
 followed by an asterisk.