Build setup allows for JDK 10 as source/test target compatibility

Includes upgrade to Groovy 2.4.15 and HtmlUnit 2.30.

Issue: SPR-16390

spring-context-support/spring-context-support.gradle

@@ -17,9 +17,9 @@ dependencies {
 	testCompile(project(":spring-context"))
 	testCompile("org.hsqldb:hsqldb:${hsqldbVersion}")
 	testCompile("org.hibernate:hibernate-validator:6.0.9.Final")
+	testCompile("javax.annotation:javax.annotation-api:1.3.2")
 	testRuntime("org.ehcache:jcache:1.0.1")
 	testRuntime("org.ehcache:ehcache:3.4.0")
 	testRuntime("org.glassfish:javax.el:3.0.1-b08")
-	testRuntime("javax.annotation:javax.annotation-api:1.3.2")
 	testRuntime("com.sun.mail:javax.mail:1.6.1")
 }