Disable javadoc linting when building with JDK 8+

Java 8 introduced new, aggressive linting of javadoc that’s enabled by
default. The linter isn’t sufficiently configurable to allow us to tune
it to meet the project’s conventions for javadoc so our only realistic
option is to disable linting.

This commit introduces a new profile to disable javadoc linting. To
maintain compatibility with JDK 7, the profile is only active when the
build’s running on JDK 8 or later.

Closes spring-projectsgh-2233

spring-boot-parent/pom.xml

@@ -572,6 +572,9 @@
 									<goal>jar</goal>
 								</goals>
 								<inherited>true</inherited>
+								<configuration>
+									<additionalparam>${javadoc.opts}</additionalparam>
+								</configuration>
 							</execution>
 						</executions>
 					</plugin>
@@ -588,6 +591,15 @@
 				</pluginRepository>
 			</pluginRepositories>
 		</profile>
+		<profile>
+			<id>disable-java8-doclint</id>
+			<activation>
+				<jdk>[1.8,)</jdk>
+			</activation>
+			<properties>
+				<javadoc.opts>-Xdoclint:none</javadoc.opts>
+			</properties>
+		</profile>
 		<profile>
 			<id>snapshot</id>
 		</profile>