Minor javadoc improvements

[keithc-ca]

Avoid < and > in javadoc; use < and > instead.

Without these changes, building openj9 javadocs for jdknext (via ibmruntimes/openj9-openjdk-jdk#210) fails:

javadoc: error - An internal exception has occurred. 
	(java.lang.NullPointerException)
Please file a bug against the javadoc tool via the Java bug reporting page
(http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com)
for duplicates. Include error messages and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.isSelfClosingAllowed(Checker.java:424)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.visitStartElement(Checker.java:382)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.visitStartElement(Checker.java:106)
	at jdk.compiler.interim/com.sun.tools.javac.tree.DCTree$DCStartElement.accept(DCTree.java:850)
	at jdk.compiler.interim/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
	at jdk.compiler.interim/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:83)
	at jdk.compiler.interim/com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:98)
	at jdk.compiler.interim/com.sun.source.util.DocTreeScanner.visitAuthor(DocTreeScanner.java:147)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.visitAuthor(Checker.java:815)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.visitAuthor(Checker.java:106)
	at jdk.compiler.interim/com.sun.tools.javac.tree.DCTree$DCAuthor.accept(DCTree.java:238)
	at jdk.compiler.interim/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
	at jdk.compiler.interim/com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:98)
	at jdk.compiler.interim/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:106)
	at jdk.compiler.interim/com.sun.source.util.DocTreeScanner.visitDocComment(DocTreeScanner.java:185)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.visitDocComment(Checker.java:269)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.visitDocComment(Checker.java:106)
	at jdk.compiler.interim/com.sun.tools.javac.tree.DCTree$DCDocComment.accept(DCTree.java:138)
	at jdk.compiler.interim/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:50)
	at jdk.compiler.interim/com.sun.tools.doclint.Checker.scan(Checker.java:231)
	at jdk.compiler.interim/com.sun.tools.doclint.DocLint.scan(DocLint.java:351)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.WorkArounds.runDocLint(WorkArounds.java:111)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.Utils.getDocCommentTree0(Utils.java:2725)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.Utils.getDocCommentTree(Utils.java:2768)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.Utils$CommentHelperCache.computeIfAbsent(Utils.java:2914)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.Utils.getCommentHelper(Utils.java:2588)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.Utils.hasBlockTag(Utils.java:2632)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.Utils.hasHiddenTag(Utils.java:1556)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.ClassTree.buildTree(ClassTree.java:175)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.util.ClassTree.<init>(ClassTree.java:119)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:204)
	at jdk.javadoc.interim/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:113)
	at jdk.javadoc.interim/jdk.javadoc.doclet.StandardDoclet.run(StandardDoclet.java:103)
	at jdk.javadoc.interim/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:555)
	at jdk.javadoc.interim/jdk.javadoc.internal.tool.Start.begin(Start.java:399)
	at jdk.javadoc.interim/jdk.javadoc.internal.tool.Start.begin(Start.java:348)
	at jdk.javadoc.interim/jdk.javadoc.internal.tool.Main.execute(Main.java:63)
	at jdk.javadoc.interim/jdk.javadoc.internal.tool.Main.main(Main.java:52)

[pshipton]

The travis build should be sufficient testing for this.