RFR: 8263640: hs_err improvement: handle class path longer than O_BUFLEN

[Calvin Cheung]

Please review this patch for handling the printing of class path with length longer than O_BUFLEN.
The bug is also reproducible using the `jcmd VM.command_line`. The new test uses `jcmd` to verify this change.

Testing: 
- [x] tiers 1,2.

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Commit messages:
 - 8263640: hs_err improvement: handle class path longer than O_BUFLEN

Changes: https://git.openjdk.java.net/jdk/pull/4616/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4616&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263640
  Stats: 92 lines in 2 files changed: 91 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4616.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4616/head:pull/4616

PR: https://git.openjdk.java.net/jdk/pull/4616