Remove xdoclint:none for < JDK 8

Author: rwinch

build.gradle

@@ -124,7 +124,9 @@ configure(subprojects - project(":spring-build-src")) { subproject ->
 		options.author = true
 		options.header = project.name
 		options.links(project.ext.javadocLinks)
-		options.addStringOption('Xdoclint:none', '-quiet')
+		if(JavaVersion.current().isJava8Compatible()) {
+			options.addStringOption('Xdoclint:none', '-quiet')
+		}
 
 		// suppress warnings due to cross-module @see and @link references;
 		// note that global 'api' task does display all warnings.
@@ -834,7 +836,9 @@ configure(rootProject) {
 		options.stylesheetFile = file("src/api/stylesheet.css")
 		options.splitIndex = true
 		options.links(project.ext.javadocLinks)
-		options.addStringOption('Xdoclint:none', '-quiet')
+		if(JavaVersion.current().isJava8Compatible()) {
+			options.addStringOption('Xdoclint:none', '-quiet')
+		}
 
 		source subprojects.collect { project ->
 			project.sourceSets.main.allJava