The JVM feature rewrite was actually somewhat of a step backwards in terms of presenting information for the user what different configure arguments do.

I've compensated for this by making it far better! :) Now we get a list like this:
  aot enable ahead of time compilation (AOT)
  cds enable class data sharing (CDS)
  compiler1 enable hotspot compiler C1
  compiler2 enable hotspot compiler C2
  dtrace enable dtrace support
  epsilongc include the epsilon (no-op) garbage collector
  g1gc include the G1 garbage collector
  graal enable Graal (jdk.internal.vm.compiler)
  jfr enable Java Flight Recorder (JFR)
  jni-check enable -Xcheck:jni support
  jvmci enable JVM Compiler Interface (JVMCI)
  jvmti enable Java Virtual Machine Tool Interface (JVM TI)
  link-time-opt enable link time optimization
  management enable java.lang.management API support
  minimal support building variant 'minimal'
  nmt include native memory tracking (NMT)
  parallelgc include the parallel garbage collector
  serialgc include the serial garbage collector
  services enable diagnostic services and client attaching
  shenandoahgc include the Shenandoah garbage collector
  static-build build static library instead of dynamic
  vm-structs export JVM structures to the Serviceablility Agent
  zero support building variant 'zero'
  zgc include the ZGC garbage collector

Also, I missed using the recommended m4_ prefix on some m4 functions. This patch also corrects this.