RFR: 8247957: remove doclint support for HTML 4 [v6]

[Yoshiki Sato]

> 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 updated the pull request incrementally with one additional commit since the last revision:

  7th: Some fixes and additional changes for 8247957

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/893/files
  - new: https://git.openjdk.java.net/jdk/pull/893/files/261f207a..8a0e1193

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=893&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=893&range=04-05

  Stats: 17 lines in 4 files changed: 11 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/893.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/893/head:pull/893

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