Java 9 support

[hcoles]

Known issues

• ASM 5.2 does not support Java 9 bytecode - ASM 6 beta should be available from central soon
• Shade plugin does not support Java 9 -> https://issues.apache.org/jira/browse/MSHADE-242
• Xstream does not support Java 9 -> java 9 + jigsaw compatibility x-stream/xstream#74
• Add Java 9 to travis matrix -> not clear if there is working support

May also be other issues that are masked by these blockers.

Suggest waiting for updates to ASM and Shade plugin and beginning to migrate away from XStream which likely has a harder and longer path to support Java 9.

[szpak]

ASM 6 beta is already available in Maven Central. Shade plugin has been also adjusted to Java 9. Issue with Xstream seems to be valid, however, there are some Java 9 (loosely) related commits in master.

[hcoles]

@szpak Master branch was updated to ASM6 a few weeks ago but I forgot to update this issue.

It all seems to work, but xstream triggers a lot of warnings.

This branch is 95% of the way to removing it -> https://github.com/hcoles/pitest/tree/no_xstream

But it it's a big change with some unexpected consequences.

Will most likely release the current master in the next few days and make a call on xstream after java 9 is out,

[hcoles]

1.2.3 has been released with ASM 6.

Leaving this issue open for now to track remaining/new Java 9 issues.

[triceo]

From my experiments, it seems like #48 is back. On Java 9, the following code shows a whole lot of survivors that aren't there when the same code is run on Java 8:

https://github.com/RoboZonky/robozonky/blob/master/robozonky-integration-zonkoid/src/main/java/com/github/robozonky/integrations/zonkoid/Util.java#L30