RFR: JDK-8201575 Allow numbers in VERSION_PRE according to JEP 223

[Magnus Ihse Bursie]

This is an old web bug. Our implementation of version parsing do not 
match the latest changes to JEP 223. Specifically, the PRE tag can now 
also include numbers, not only letters.

And yes, this is horribly unreadable.

Some people, when confronted with a problem, think “I know,
I'll use regular expressions.”  Now they have two problems.
/Jamie Zawinski

Bug: https://bugs.openjdk.java.net/browse/JDK-8201575
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8201575-numbers-in-version-pre/webrev.01

/Magnus