RFR: 8247957: remove doclint support for HTML 4

[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

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Commit messages:
 - 3rd: 8247957 and 8256312
 - Merge branch 'master' into JDK-8247957_2
 - 8247957: remove doclint support for HTML 4
 - 8247957: remove doclint support for HTML 4

Changes: https://git.openjdk.java.net/jdk/pull/893/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=893&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8247957
  Stats: 1445 lines in 54 files changed: 418 ins; 744 del; 283 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