RFR: JDK-8087328: Move debuglevel info in version string from PRE to OPT

[Erik Joelsson]

Hello,

Please review this change to the new build number implementation in 
project Verona. This change is intended to go into the verona forest for 
now until it's time for integration into jdk9.

In Magnus' original version string implementation, the debuglevel 
information is encoded into the PRE string. According to the latest 
status of JEP-223, it should rather be a part of the OPT string. In this 
patch, I have made that move.

This means that the (relevant) configure options have changed from:

--with-version-pre-base
--with-version-pre-debuglevel
--with-version-opt

into:

--with-version-pre
--with-version-opt-base
--with-version-opt-debuglevel

I also had to introduce some way of telling the OPT_BASE string apart 
from the OPT_DEBUGLEVEL string when parsing a full version string. In 
the PRE string, the separator was a '.' but since that character is a 
valid part of the OPT string, something else is needed. I went with 
underscore '_' for now.

Bug: https://bugs.openjdk.java.net/browse/JDK-8087328
Webrev: http://cr.openjdk.java.net/~erikj/8087328/webrev.01/

/Erik