Summary
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Remove support for the now-unsupported "old" doclet API

Problem
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The version of the javadoc "doclet" API that was in use up to JDK 8 was superseded by a new API in JDK 9, and a corresponding new "Standard Doclet". The old Standard Doclet has already been removed; the old API has been retained somewhat longer in case there are other doclets in use using the API. However, the API is old, unsupported and does not support newer language features, like modules, and newer javadoc tags.

Solution
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Remove the old API in com.sun.javadoc.*, and the old entry point, com.sun.tools.javadoc.Start

An off-brand use of the old API was as an early "Language Model" API. But javax.lang.model has been available as a first-class supported Language Model API since JDK 6. 


Specification
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The primary change is about removing the old API. There are some residual references in the remaining API that need to be updated.

Specification attached, also available at 
 
*   <http://cr.openjdk.java.net/~pmuthuswamy/8215584/specdiff//overview-summary.html>
*   <http://cr.openjdk.java.net/~pmuthuswamy/8215584/specdiff_plain_profile/specdiff-summary.html>
    (shows changes in module declaration)