RFR: 8247957: remove doclint support for HTML 4 [v3]

[Jonathan Gibbons]

On Thu, 17 Dec 2020 01:40:14 GMT, Yoshiki Sato <ysatowse at openjdk.org> wrote:

>> HTML4 is no longer supported in javadoc.
>> 
>> doclint needs to drop HTML4 support as well.
>> The changes consist of:
>> * Removing jdk.javadoc.internal.doclint.HtmlVersion and its references.
>> * Sorting out supported tags and attributes in HTML5 (including fix incorrect permission of valign in TH, TR, TD, THEAD and TBODY)
>> * Modifying test code and expected outputs to be checked in HTML5
>
> Yoshiki Sato has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   8257204 and 8256313
>   8257204: Remove usage of -Xhtmlversion option from javac
>   8256313: JavaCompilation.gmk needs to be updated not to use --doclint-format html5 option

Mostly OK; some minor suggestions

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclint/resources/doclint.properties line 36:

> 34: dc.attr.img.border.not.number = attribute "border" for img is not a number
> 35: dc.attr.table.border.not.valid = attribute "border" for table only accepts "" or "1", use CSS instead: {0}
> 36: dc.attr.table.border.not.number = attribute "border" for table is not a number

suggest dropping "use CSS instead"

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PR: https://git.openjdk.java.net/jdk/pull/893