Upgrade to Netty 4.1.31 and Undertow 2.0.15

Author: jhoeller

build.gradle

@@ -37,15 +37,15 @@ ext {
 	junit5Version        = "5.3.1"
 	kotlinVersion        = "1.2.71"
 	log4jVersion         = "2.11.1"
-	nettyVersion         = "4.1.30.Final"
+	nettyVersion         = "4.1.31.Final"
 	reactorVersion       = "Californium-SR2"
 	rxjavaVersion        = "1.3.8"
 	rxjavaAdapterVersion = "1.2.1"
 	rxjava2Version       = "2.2.3"
 	slf4jVersion         = "1.7.25"	  // spring-jcl + consistent 3rd party deps
 	tiles3Version        = "3.0.8"
 	tomcatVersion        = "9.0.12"
-	undertowVersion      = "2.0.14.Final"
+	undertowVersion      = "2.0.15.Final"
 
 	gradleScriptDir = "${rootProject.projectDir}/gradle"
 	withoutJclOverSlf4J = {