Upgrade to Objenesis 2.6

Includes latest dependency updates (Groovy 2.4.12, Jackson 2.8.9, Jetty 9.4.6, Netty 4.1.12, Tomcat 8.5.16)

Issue: SPR-15600

build.gradle

@@ -40,7 +40,7 @@ configure(allprojects) { project ->
 	ext.ejbVersion           = "3.0"
 	ext.fileuploadVersion    = "1.3.2"
 	ext.freemarkerVersion    = "2.3.23"
-	ext.groovyVersion        = "2.4.11"
+	ext.groovyVersion        = "2.4.12"
 	ext.gsonVersion          = "2.8.0"
 	ext.guavaVersion         = "20.0"
 	ext.hamcrestVersion      = "1.3"
@@ -52,17 +52,17 @@ configure(allprojects) { project ->
 	ext.hsqldbVersion        = "2.3.4"
 	ext.httpasyncVersion     = "4.1.3"
 	ext.httpclientVersion    = "4.5.3"
-	ext.jackson2Version      = "2.8.7"
+	ext.jackson2Version      = "2.8.9"
 	ext.jasperreportsVersion = "6.2.1"  // our tests fail with JR-internal NPEs against 6.2.2 and higher
 	ext.javamailVersion      = "1.5.6"
 	ext.jettyVersion         = "9.3.14.v20161028"  // as of 9.3.15, Jetty has hard Servlet 3.1 requirement
-	ext.jetty94Version       = "9.4.5.v20170502"  // for spring-websocket support, optimized for Jetty 9.4
+	ext.jetty94Version       = "9.4.6.v20170531"  // for spring-websocket support, optimized for Jetty 9.4
 	ext.jodaVersion          = "2.9.9"
 	ext.jrubyVersion         = "1.7.26"  // JRuby 9000 primarily supported through JSR-223 (StandardScriptFactory)
 	ext.jtaVersion           = "1.2"
 	ext.junitVersion         = "4.12"
 	ext.log4jVersion         = "1.2.17"
-	ext.nettyVersion         = "4.1.11.Final"
+	ext.nettyVersion         = "4.1.12.Final"
 	ext.okhttpVersion        = "2.7.5"
 	ext.okhttp3Version       = "3.7.0"
 	ext.openjpaVersion       = "2.4.1"
@@ -75,7 +75,7 @@ configure(allprojects) { project ->
 	ext.testngVersion        = "6.9.10"
 	ext.tiles2Version        = "2.2.2"
 	ext.tiles3Version        = "3.0.7"
-	ext.tomcatVersion        = "8.5.15"
+	ext.tomcatVersion        = "8.5.16"
 	ext.tyrusVersion         = "1.3.5"  // constrained by WebLogic 12.1.3 support
 	ext.undertowVersion      = "1.3.30.Final"
 	ext.xmlunitVersion       = "1.6"
@@ -294,7 +294,7 @@ project("spring-core") {
 	// further transformed by the JarJar task to depend on org.springframework.asm; this
 	// avoids including two different copies of asm unnecessarily.
 	def cglibVersion = "3.2.5"
-	def objenesisVersion = "2.5.1"
+	def objenesisVersion = "2.6"
 
 	configurations {
 		jarjar