epson2: Add Expression 12000XL / DS-G20000 as supported

Also removed stale comment in epson2.desc.

See https://lists.alioth.debian.org/pipermail/sane-devel/2017-November/035744.html

backend/epson2_usb.c

@@ -31,6 +31,7 @@ SANE_Word sanei_epson_usb_product_ids[] = {
   0x138, /* ES-H7200, GT-20000 */
   0x14b, /* ES-G11000, Expression 11000XL */
   0x151, /* GT-X980, Perfection V800 Photo, Perfection V850 Pro */
+  0x15b, /* DS-G20000, Expression 12000XL */
   0x801, /* CC-600PX, Stylus CX5100, Stylus CX5200 */
   0x802, /* CC-570L, Stylus CX3100, Stylus CX3200 */
   0x805, /* Stylus CX6300, Stylus CX6400 */

doc/descriptions/epson2.desc

@@ -6,8 +6,6 @@
 ;
 ; This file is derived from epkowa.desc, Copyright (C) Olaf Meeuwissen,
 ; distributed with "Image Scan!" and released under GPL.
-;
-; DO NOT EDIT - It's automatically generated.
 
 :backend "epson2"
 :version "1.0.124 (unmaintained)"
@@ -163,6 +161,11 @@
 :status     :unsupported
 :comment    "supported by the epkowa backend plus non-free interpreter"
 
+:model      "DS-G20000"
+:interface  "USB"
+:usbid      "0x04b8" "0x015b"
+:status     :good
+
 :model      "EP-702A"
 :interface  "USB"
 :usbid      "0x04b8" "0x0850"
@@ -590,6 +593,12 @@
 :status     :good
 :comment    "overseas version of the ES-G11000"
 
+:model      "Expression 12000XL"
+:interface  "USB"
+:usbid      "0x04b8" "0x015b"
+:status     :good
+:comment    "overseas version of the DS-G20000"
+
 :model      "F-3200"			; product spec (JP)
 :interface  "USB IEEE1394"
 :usbid      "0x04b8" "0x080a"