Auto-generate file header comments in Unicode mapping files.

Some of the Unicode/*.map files had identification comments added to them,
evidently by hand.  Others did not.  Modify the generating scripts to
produce these comments automatically, and update the generated files that
lacked them.

This is just minor cleanup as a by-product of trying to verify that the
*.map files can indeed be reproduced from authoritative data.  There are a
depressingly large number that fail to reproduce from the claimed sources.
I have not touched those in this commit, except for the JIS 2004-related
files which required only a single comment update to match.

Since this only affects comments, no need to consider a back-patch.

src/backend/utils/mb/Unicode/utf8_to_win1257.map

+/* src/backend/utils/mb/Unicode/utf8_to_win1257.map */
+
 static const pg_utf_to_local ULmapWIN1257[ 116 ] = {
   {0xc2a0, 0x00a0},
   {0xc2a2, 0x00a2},

src/backend/utils/mb/Unicode/utf8_to_win1258.map

+/* src/backend/utils/mb/Unicode/utf8_to_win1258.map */
+
 static const pg_utf_to_local ULmapWIN1258[ 119 ] = {
   {0xc2a0, 0x00a0},
   {0xc2a1, 0x00a1},

src/backend/utils/mb/Unicode/utf8_to_win866.map

+/* src/backend/utils/mb/Unicode/utf8_to_win866.map */
+
 static const pg_utf_to_local ULmapWIN866[ 128 ] = {
   {0xc2a0, 0x00ff},
   {0xc2a4, 0x00fd},

src/backend/utils/mb/Unicode/utf8_to_win874.map

+/* src/backend/utils/mb/Unicode/utf8_to_win874.map */
+
 static const pg_utf_to_local ULmapWIN874[ 97 ] = {
   {0xc2a0, 0x00a0},
   {0xe0b881, 0x00a1},

src/backend/utils/mb/Unicode/win1250_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1250_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1250[ 123 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win1251_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1251_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1251[ 127 ] = {
   {0x0080, 0xd082},
   {0x0081, 0xd083},

src/backend/utils/mb/Unicode/win1252_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1252_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1252[ 123 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win1253_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1253_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1253[ 111 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win1254_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1254_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1254[ 121 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win1255_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1255_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1255[ 105 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win1256_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1256_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1256[ 128 ] = {
   {0x0080, 0xe282ac},
   {0x0081, 0xd9be},

src/backend/utils/mb/Unicode/win1257_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1257_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1257[ 116 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win1258_to_utf8.map

+/* src/backend/utils/mb/Unicode/win1258_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN1258[ 119 ] = {
   {0x0080, 0xe282ac},
   {0x0082, 0xe2809a},

src/backend/utils/mb/Unicode/win866_to_utf8.map

+/* src/backend/utils/mb/Unicode/win866_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN866[ 128 ] = {
   {0x0080, 0xd090},
   {0x0081, 0xd091},

src/backend/utils/mb/Unicode/win874_to_utf8.map

+/* src/backend/utils/mb/Unicode/win874_to_utf8.map */
+
 static const pg_local_to_utf LUmapWIN874[ 97 ] = {
   {0x0080, 0xe282ac},
   {0x0085, 0xe280a6},