RFR: 8244669: convert clhsdb "mem" command from javascript to java [v5]

[Chris Plummer]

> clhsdb lost support for the "mem" command when javascript support was removed from SA. This PR is re-adding it by implementing it in Java. The description of the CR contains all the details.
> 
> Regarding the clhsdb.html changes for the "examine" command, they are just correctly specifying the existing syntax. No change was actually made to the syntax.
> 
> The changes made to the "examine" command are part of a consolidation effort to better share code between "examine" and "mem". "examine" has no functional changes.

Chris Plummer has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:

 - Merge
 - Minor improvements to help text for mem and examine.
 - Fix issue with address range patterns. For some reason they have always allowed some extra lower case letters at the end of the pattern that just get ignored. I removed support for this since sometimes it resulted in bad address ranges producing an exception rather than a usage() message.
 - Fix missing return after calling usage()
 - Change output string we look for so it passes on all platforms.
 - Add support for clhsdb 'mem' command.

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Changes: https://git.openjdk.java.net/jdk/pull/6902/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6902&range=04
  Stats: 157 lines in 3 files changed: 121 ins; 28 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6902.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6902/head:pull/6902

PR: https://git.openjdk.java.net/jdk/pull/6902