fix spelling of offset since that is what is used in the body...

usr.bin/hexdump/hexdump.1

@@ -28,7 +28,7 @@
 .\"	@(#)hexdump.1	8.2 (Berkeley) 4/18/94
 .\" $FreeBSD$
 .\"
-.Dd February 18, 2010
+.Dd October 29, 2014
 .Dt HEXDUMP 1
 .Os
 .Sh NAME
@@ -41,7 +41,7 @@
 .Op Fl f Ar format_file
 .Op Fl n Ar length
 .Bk -words
-.Op Fl s Ar skip
+.Op Fl s Ar offset
 .Ek
 .Ar
 .Nm hd
@@ -50,7 +50,7 @@
 .Op Fl f Ar format_file
 .Op Fl n Ar length
 .Bk -words
-.Op Fl s Ar skip
+.Op Fl s Ar offset
 .Ek
 .Ar
 .Sh DESCRIPTION