(check-doc): Use "diff -c" instead of "diff -u" for increased portability.

doc/Makefile.am

-# $Id: Makefile.am,v 1.45 2002/08/16 15:23:27 ceder Exp $
+# $Id: Makefile.am,v 1.46 2002/08/16 18:14:57 ceder Exp $
 # Copyright (C) 1998-1999, 2001-2002  Lysator Academic Computer Association.
 #
 # This file is part of the LysKOM server.
@@ -290,7 +290,7 @@ check-doc: Protocol-A.notab lyskomd.notab info
 	## check that they are expected, and then manually update
 	## constructs.expected.  Please be careful when you examine the
 	## diff.
-	diff -u $(srcdir)/constructs.expected constructs-@.tmp
+	diff -c $(srcdir)/constructs.expected constructs-@.tmp
 
 	## Check @rarg{} and @aarg{} constructs.  They are only allowed
 	## to refer to named arguments of the call they are documenting.