RFR: 8277165: jdeps --multi-release --print-module-deps fails if module-info.class in different versioned directories [v2]

[Mandy Chung]

> jdeps intends to report an error if there are multiple versions of the same class being parsed.   module-info.class should be excluded from such detection.
> 
> This patch also fixes a data race in `VersionHelper::set` and also unwraps the `ExecutionException` when FutureTask of parsing the classes throws an exception to report `MultiReleaseException` properly.

Mandy Chung has updated the pull request incrementally with one additional commit since the last revision:

  minor fix to avoid casting

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6530/files
  - new: https://git.openjdk.java.net/jdk/pull/6530/files/2cb770d4..2045e372

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6530&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6530&range=00-01

  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6530.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6530/head:pull/6530

PR: https://git.openjdk.java.net/jdk/pull/6530