RFR: JDK-8201483 Make it possible to disable JVM features

Thu Apr 12 11:39:20 UTC 2018

It is currently easy to add new JVM features to the JVM build, but it is 
not possible to remove features.

With this change, features can be both added or removed from the default 
set. They are added using --with-jvm-features=f1,f2 and removed using 
--with-jvm-features=-f1,-f2. The syntax can be combined, so 
--with-jvm-features=dtrace,-nmt will enable dtrace but disable native 
memory tracking.

I also included some additional code cleanup and fixes, such as printing 
the JVM feature set at the summary.

Bug: https://bugs.openjdk.java.net/browse/JDK-8201483
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8201483-disable-JVM-features/webrev.01