Bug 958 - Add support for OpenJDK version notation

Manu <puybaret@eteks.com>:

In OpenJDK, Java version notation is a little different from Oracle JDK one:
OpenJDK uses "-u" instead of "_" to separate the version number from the update number, i.e. "1.7.0-u60-b04" vs "1.7.0_60-ea".
That would be nice to take this into account in the static initializer of jogamp.common.os.PlatformPropsImpl class. You could simply replace the line:
  final int usIdx = JAVA_VERSION.lastIndexOf("_");
by:
  final int usIdx = JAVA_VERSION.replace("-u", "_").lastIndexOf("_");
If you want to program it better, you can also test the "java.runtime.name" property that returns "OpenJDK Runtime Environment" for OpenJDK.

See also bug #944 https://jogamp.org/bugzilla/show_bug.cgi?id=944

+++

Done .. avoding the replace op.