[9] Review request: 8176538: Fix errors in JavaFX API docs when using 'javadoc -html5'

[Kevin Rushforth]

Please review the following javadoc-only change to make the FX API docs 
doclint clean with -html5 :

https://bugs.openjdk.java.net/browse/JDK-8176538
http://cr.openjdk.java.net/~kcr/8176538/webrev.00/
I verified that with these changes we are doclint clean both with and 
without the -html5 option.

Thanks.

-- Kevin