8153243: make docs should generate JShell API docs

Summary: Tweaking JShell javadoc so that it can be built without warnings/errors.
Reviewed-by: rfield, erikj

langtools/src/jdk.jshell/share/classes/jdk/jshell/Diag.java

@@ -55,8 +55,7 @@ public abstract class Diag {
      * <p>{@code getPosition() <= getEndPosition()}
      *
      * @return character offset from beginning of source; {@link
-     * #NOPOS} if {@link #getSource()} would return {@code null} or if
-     * no location is suitable
+     * #NOPOS} if the position is not available.
      */
     public abstract long getPosition();
 

langtools/src/jdk.jshell/share/classes/jdk/jshell/JShell.java

@@ -384,7 +384,7 @@ public class JShell implements AutoCloseable {
     /**
      * The specified path is added to the end of the classpath used in eval().
      * Note that the unnamed package is not accessible from the package in which
-     * {@link JShell#eval()} code is placed.
+     * {@link JShell#eval(String)} code is placed.
      * @param path the path to add to the classpath.
      */
     public void addToClasspath(String path) {