MDL-67414 adodb: Backport upstream fix for PostgreSQL 12.x

Upstream: https://github.com/ADOdb/ADOdb/commit/a4876f100602c2ce4760bb72d3050f73387adcca
          pgsql: stop using obsolete pg_attrdef.adsrc column

lib/adodb/drivers/adodb-postgres8.inc.php

@@ -20,6 +20,12 @@ class ADODB_postgres8 extends ADODB_postgres7
 {
 	var $databaseType = 'postgres8';
 
+	// From PostgreSQL 8.0 onwards, the adsrc column used in earlier versions to
+	// retrieve the default value is obsolete and should not be used (see #562).
+	var $metaDefaultsSQL = "SELECT d.adnum as num, pg_get_expr(d.adbin, d.adrelid) as def
+		FROM pg_attrdef d, pg_class c 
+		WHERE d.adrelid=c.oid AND c.relname='%s' 
+		ORDER BY d.adnum";
 
 	/**
 	 * Retrieve last inserted ID

lib/adodb/readme_moodle.txt

@@ -31,5 +31,6 @@ Our changes:
  * MDL-52286 Added muting erros in ADORecordSet::__destruct().
    Check if fixed upstream during the next upgrade and remove this note. (8638b3f1441d4b928)
  * MDL-67034 Fixes to make the library php74 compliant.
+ * MDL-67414 Fix to make the library PostgreSQL 12.x compliant (upstream: a4876f100602c2ce4).
 
-skodak, iarenaza, moodler, stronk7, abgreeve, lameze, ankitagarwal, marinaglancy
+skodak, iarenaza, moodler, stronk7, abgreeve, lameze, ankitagarwal, marinaglancy, matteo