Fix description of scanadf regarding sane-hp

Changelog

@@ -1,3 +1,8 @@
+2008-07-03 Peter Kirchgeßner <peter@kirchgessner.net>
+	* doc/scanadf.man: Fix description of options for sane-hp-backend.
+	  A patch for sane-hp to be used with scanadf is not necessary
+	  and --source=ADF should be specified.
+
 2008-06-06 Stéphane Voltz <stef.dev@free.fr>
 	* src/gtkglue.c src/preview.c src/progress.c src/progress.h
 	  src/scanadf.c src/xcam.c src/xscanimage.c configure.in configure: