Set the character set before making a connection

Ideally the character set should be set with the connection, and so this is
exactly what's being done now.

And now the character set code is attempted to be generalised.

lib/util/util.php

@@ -2390,6 +2390,15 @@ function common_compatible_license($from, $to)
     return ($from == $to);
 }
 
+/**
+ * returns the character set name used for the current DBMS
+ */
+function common_database_charset(): string
+{
+    $schema = Schema::get();
+    return $schema->charset();
+}
+
 /**
  * returns a quoted table name
  */