GRIDMATRIX/HANXIN/QRCODE: set Project Nayuki stuff copyright 2019

as that's when it was adapted
debian/copyright: incorporate above & remove "Copyright (C)"
  prefixes to make a bit more like the upstream Debian one

backend/gridmtx.c

@@ -126,7 +126,7 @@ static int gm_in_numeral(const unsigned int ddata[], const int length, const int
 static const char gm_debug_modes[6][5] = { "HAN ", "NUM ", "LWR ", "UPR ", "MXD ", "BYT " };
 
 /* Calculate optimized encoding modes. Adapted from Project Nayuki */
-/* Copyright (c) Project Nayuki. (MIT License) See qr.c for detailed notice */
+/* Copyright (c) 2019 Project Nayuki. (MIT License) See qr.c for detailed notice */
 /* SPDX-License-Identifier: MIT */
 static void gm_define_modes(char *modes, const unsigned int ddata[], const int length, const int debug_print) {
     /* Must be in same order as GM_H etc */

backend/hanxin.c

@@ -352,7 +352,7 @@ static int hx_in_fourbyte(const unsigned int ddata[], const int length, const in
 #define HX_NUM_MODES 7
 
 /* Calculate optimized encoding modes. Adapted from Project Nayuki */
-/* Copyright (c) Project Nayuki. (MIT License) See qr.c for detailed notice */
+/* Copyright (c) 2019 Project Nayuki. (MIT License) See qr.c for detailed notice */
 /* SPDX-License-Identifier: MIT */
 static void hx_define_modes(char *modes, const unsigned int ddata[], const int length, const int debug_print) {
     /* Must be in same order as HX_N etc */

backend/qr.c

@@ -218,7 +218,7 @@ static unsigned int *qr_head_costs(unsigned int state[11]) {
 static void qr_define_modes(char modes[], const unsigned int ddata[], const int length, const int gs1,
             const int version, const int debug_print) {
     /*
-     * Copyright (c) Project Nayuki. (MIT License)
+     * Copyright (c) 2019 Project Nayuki. (MIT License)
      * https://www.nayuki.io/page/qr-code-generator-library
      *
      * Permission is hereby granted, free of charge, to any person obtaining a copy of