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