Summary
-------
Define `ElementScanner14` to visit type parameters; surprisingly, type parameters and not visited by the previously available scanners.

Problem
-------

Surprising behavior in `javax.lang.model` utility classes. At least one scanner class with the new functionality was written as part of the `javac` implementation.

Solution
--------

Add overrides for the methods visiting executables and types to visit type parameters, if present.

Specification
-------------

    --- old/src/java.compiler/share/classes/javax/lang/model/util/ElementScanner14.java	2019-12-04 19:16:42.857000999 -0800
    +++ new/src/java.compiler/share/classes/javax/lang/model/util/ElementScanner14.java	2019-12-04 19:16:42.601000999 -0800
    @@ -121,6 +123,48 @@
         }
     
         /**
    +     * {@inheritDoc}
    +     *
    +     * @implSpec This implementation scans the type parameters, if
    +     * any, and then the enclosed elements.
    +     * 
    +     *
    +     * @param e  {@inheritDoc}
    +     * @param p  {@inheritDoc}
    +     * @return the result of scanning
    +     */
    +    @Override
    +    public R visitType(TypeElement e, P p) {
    +        return scan(createScanningList(e, e.getEnclosedElements()), p);
    +    }
    +
    +    /**
    +     * {@inheritDoc}
    +     *
    +     * @implSpec This implementation first scans the type parameters, if any, and then
    +     * the parameters.
    +     *
    +     * @param e  {@inheritDoc}
    +     * @param p  {@inheritDoc}
    +     * @return the result of scanning
    +     */
    +    public R visitExecutable(ExecutableElement e, P p) {
    +        return scan(createScanningList(e, e.getParameters()), p);
    +    }
    +