Updates for 2.4.2 release.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012447
Adds an option for formatter display name.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012450
Rescue syntax highlighter exceptions.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012451
Adds experimental support for Markdown formatting with redcarpet (#15520).

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012452
Don't load redcarpet with JRuby.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4012453