Upgrade to Log4J 2.9 (and Undertow 1.4.20)

Author: jhoeller

build.gradle

@@ -56,7 +56,7 @@ configure(allprojects) { project ->
 	ext.junitPlatformVersion = '1.0.0-RC3'
 	ext.junitVintageVersion  = "4.12.0-RC3"
 	ext.kotlinVersion        = '1.1.4-3'
-	ext.log4jVersion         = '2.8.2'
+	ext.log4jVersion         = '2.9.0'
 	ext.nettyVersion         = "4.1.15.Final"
 	ext.okhttp3Version       = "3.8.1"
 	ext.reactorVersion       = "Bismuth-BUILD-SNAPSHOT"
@@ -66,7 +66,7 @@ configure(allprojects) { project ->
 	ext.slf4jVersion         = "1.7.25"
 	ext.tiles3Version        = "3.0.7"
 	ext.tomcatVersion        = "8.5.20"
-	ext.undertowVersion      = "1.4.19.Final"
+	ext.undertowVersion      = "1.4.20.Final"
 
 	ext.gradleScriptDir = "${rootProject.projectDir}/gradle"