RFR: 8262520: Add CLHSDB command to connect to debug server

[Yasumasa Suenaga]

`attach` command on CLHSDB supports to attach live process (PID) and coredump, but it cannot connect to debug server. CLHSDB does not have a command to connect to debug server.

Other jhsdb commands (jstack, jmap, etc...) can connect debug server via `--connect` option, so CLHSDB should connect to it.

After this change, you can connect to debug server with 'connect <hostname>'.

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Commit messages:
 - Skip ClhsdbConnect.java if it runs on OS X and the user is not root
 - 8262520: Add CLHSDB command to connect to debug server

Changes: https://git.openjdk.java.net/jdk/pull/2773/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2773&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262520
  Stats: 138 lines in 4 files changed: 133 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2773.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2773/head:pull/2773

PR: https://git.openjdk.java.net/jdk/pull/2773