Add contrib/isn module for ISBN/ISSN/EAN13/etc product numbers, and

remove the old isbn_issn module which is about to be obsoleted by EAN13.
contrib/isn is by Germán Méndez Bravo.  Our thanks to Garrett A. Wollman
for having written the original isbn_issn module.

contrib/isn/ISSN.h

@@ -0,0 +1,49 @@
+/* 
+ * ISSN.h
+ *	  PostgreSQL type definitions for ISNs (ISBN, ISMN, ISSN, EAN13, UPC)
+ *
+ * Information recompiled by Kronuz on November 12, 2004
+ * http://www.issn.org/
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/contrib/isn/ISSN.h,v 1.1 2006/09/09 04:07:52 tgl Exp $
+ *
+ * 1144-875X <=> 1144875(X) <=> 1144875 <=> (977)1144875 <=> 9771144875(00) <=> 977114487500(7) <=> 977-1144-875-00-7
+ *
+ * 
+ * ISSN         1   1   4    4    8    7    5
+ * Weight       8   7   6    5    4    3    2 
+ * Product      8 + 7 + 24 + 20 + 32 + 21 + 10 = 122
+ *              122 / 11 = 11 remainder 1
+ * Check digit  11 - 1 = 10 = X
+ * => 1144-875X
+ * 
+ * ISSN         9   7    7   1   1   4    4   8    7   5    0   0
+ * Weight       1   3    1   3   1   3    1   3    1   3    1   3
+ * Product      9 + 21 + 7 + 3 + 1 + 12 + 4 + 24 + 7 + 15 + 0 + 0 = 103
+ *              103 / 10 = 10 remainder 3
+ * Check digit  10 - 3 = 7
+ * => 977-1144875-00-7 ??  <- suplemental number (number of the week, month, etc.)
+ *                ^^ 00 for non-daily publications (01=Monday, 02=Tuesday, ...)
+ *
+ * The hyphenation is always in after the four digits of the ISSN code.
+ *
+ */
+
+/* where the digit set begins, and how many of them are in the table */
+const unsigned ISSN_index[10][2] = {
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+	{0,		1},
+};
+const char *ISSN_range[][2] = {
+	{"0000-000", "9999-999"},
+	{NULL, NULL}
+};