RFR: JDK-8214720 Add pandoc filter to improve html man page output

Mon Dec 3 17:42:19 UTC 2018

The html output of man pages looks weird due to the metadata header 
required by pandoc to generate proper man pages. We should add a pandoc 
filter for html output as well.

The actual javascript filter implementation was graciously provided to 
me by Jon.

Bug: https://bugs.openjdk.java.net/browse/JDK-8214720
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8214720-pandoc-filter-for-html-manpages/webrev.01

/Magnus