Support Tomcat 9 and Undertow 2

Closes gh-11749
Closes gh-12243

spring-boot-project/spring-boot-starters/spring-boot-starter-jetty/pom.xml

@@ -13,6 +13,7 @@
 		alternative to spring-boot-starter-tomcat</description>
 	<properties>
 		<main.basedir>${basedir}/../../..</main.basedir>
+		<servlet-api.version>3.1.0</servlet-api.version>
 	</properties>
 	<dependencies>
 		<dependency>

spring-boot-project/spring-boot-starters/spring-boot-starter-undertow/pom.xml

@@ -25,7 +25,7 @@
 			<exclusions>
 				<exclusion>
 					<groupId>org.jboss.spec.javax.servlet</groupId>
-					<artifactId>jboss-servlet-api_3.1_spec</artifactId>
+					<artifactId>jboss-servlet-api_4.0_spec</artifactId>
 				</exclusion>
 			</exclusions>
 		</dependency>