Fix #12772: Add function to handle CSV formatting of sponsorship totals

When exporting issues in CSV format a fatal error is thrown if the
export includes sponsorship totals. This is due to a missing
csv_format_sponsorship_total function.

Signed-off-by: David Hicks <hickseydr@optusnet.com.au>

core/csv_api.php

@@ -412,3 +412,13 @@ function csv_format_due_date( $p_due_date ) {
 		$s_date_format = config_get( 'short_date_format' );
 	return csv_escape_string( date( $s_date_format, $p_due_date ) );
 }
+
+/**
+ * return the sponsorship total for an issue
+ * @param int $p_sponsorship_total
+ * @return string
+ * @access public
+ */
+function csv_format_sponsorship_total( $p_sponsorship_total ) {
+	return number_format( $p_sponsorship_total );
+}