Update to Spring Framework 4.3.18.RELEASE

Fixes: gh-5437

Author: rwinch

build.gradle

@@ -30,7 +30,7 @@ allprojects {
 
 	ext.releaseBuild = version.endsWith('RELEASE')
 	ext.snapshotBuild = version.endsWith('SNAPSHOT')
-	ext.springVersion = '4.3.17.RELEASE'
+	ext.springVersion = '4.3.18.RELEASE'
 	ext.springLdapVersion = '2.3.2.RELEASE'
 
 	group = 'org.springframework.security'