[9] Review request: 8151565: Exclude FX class files from javadoc classpath to workaround JDK-8151191

[Kevin Rushforth]

Chien,

Please review the following change to workaround a JDK 9 javac bug when 
generating our javadocs"

https://bugs.openjdk.java.net/browse/JDK-8151565
http://cr.openjdk.java.net/~kcr/8151565/webrev.00/

-- Kevin