Update the changelog

Signed-off-by: Jaime Pérez Crespo <jaime.perez@uninett.no>

docs/simplesamlphp-changelog.md

@@ -6,6 +6,16 @@ SimpleSAMLphp changelog
 This document lists the changes between versions of SimpleSAMLphp.
 See the upgrade notes for specific information about upgrading.
 
+## Versino 1.18.3
+
+Released 2019-12-09
+
+  * Fixed an issue with several modules being enabled by default (#1257).
+  * Fixed an issue with metadata generation for trusted entities (#1247, #1251).
+
+### ldap
+  * Fixed an issue affecting the installation in case-insensitive file systems (#1253).
+
 ## Version 1.18.2
 
 Released 2019-11-26