RFR: 8179413: Fix remaining minor HTML5 issues in java.base module

[Jonathan Gibbons]

Please review a handful of small changes that were not caught be the 
earlier bulk updates. Unlike those earlier updates, these few were 
determined manually.

After these minor changes, all remaining issues in java.base are related 
to the use and appearance of tables.

JBS: https://bugs.openjdk.java.net/browse/JDK-8179413
Webrev: http://cr.openjdk.java.net/~jjg/8179413/webrev/index.html

-- Jon