Clean up the remaining doclint problems in java.util.

These depend on JDK-8020556

src/share/classes/java/util/Optional.java:279: warning: no @throws for X
    public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X {
                                   ^
src/share/classes/java/util/OptionalDouble.java:176: error: reference not found
     * @throws X if there is no value present
       ^
src/share/classes/java/util/OptionalDouble.java:180: warning: no @throws for X
    public<X extends Throwable> double orElseThrow(Supplier<X> exceptionSupplier) throws X {
                                       ^
src/share/classes/java/util/OptionalInt.java:176: error: reference not found
     * @throws X if there is no value present
       ^
src/share/classes/java/util/OptionalInt.java:180: warning: no @throws for X
    public<X extends Throwable> int orElseThrow(Supplier<X> exceptionSupplier) throws X {
                                    ^
src/share/classes/java/util/OptionalLong.java:176: error: reference not found
     * @throws X if there is no value present
       ^
src/share/classes/java/util/OptionalLong.java:180: warning: no @throws for X
    public<X extends Throwable> long orElseThrow(Supplier<X> exceptionSupplier) throws X {
                                     ^
and these depend on JDK-8020313

src/share/classes/java/util/PropertyResourceBundle.java:64: error: anchor already defined: sample
 * The following <a name="sample">example</a> shows a member of a resource
                    ^
src/share/classes/java/util/Vector.java:48: error: anchor already defined: fail-fast
 * <p><a name="fail-fast">
         ^

Note that the errors in PropertyResourceBundle and Vector should just "disappear" when JDK-8020313 is fixed.