RFR: JDK-8245096 Better windows environment output in configure

[Magnus Ihse Bursie]

Unify and clean up windows environment output in configure
Bug: https://bugs.openjdk.java.net/browse/JDK-8245096
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8245096-better-windows-version/webrev.01

/Magnus