The current javadoc generation first creates the coredocs Javadoc, and
after that all the remaining javadoc instances.
This dependency is not really needed, all that is required is that the
remaining javadoc instances gets a proper pointer to a package-list file
for coredocs. Fixing that will allow them to run in parallel with the
coredoc generation.
In addition to this performance fix, I've also cleaned up the (now
unnecessary) logic of storing the javadoc command line in
.options/.packages files.
Bug: https://bugs.openjdk.java.net/browse/JDK-8170077
WebRev:
http://cr.openjdk.java.net/~ihse/JDK-8170077-parallelize-javadoc/webrev.01
/Magnus
