RFR: JDK-8137259 configure needs to parse Verona-style version strings for bootjdk

[Magnus Ihse Bursie]

Normally, the JDK should be built by a JDK from previous version (e.g. 
JDK8 for JDK9). However, building with JDK9 on JDK9 is (somewhat) supported.

A JDK9 bootjdk with the new Verona-style version string will currently 
not be recognized by configure.

This fix will be pushed to verona/stage.

Bug: https://bugs.openjdk.java.net/browse/JDK-8137259
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8137259-support-verona-style-bootjdk/webrev.01

/Magnus