RFR: 8181290 Invalid HTML 5 in core-libs docs

[Jonathan Gibbons]

Please review a small set of fixes for HTML 5 compliance which slipped 
through the previous rounds of updates.

JBS: https://bugs.openjdk.java.net/browse/JDK-8181290
Webrev:
    http://cr.openjdk.java.net/~jjg/8181290/corba.webrev.00/
    http://cr.openjdk.java.net/~jjg/8181290/jdk.webrev.00/

-- Jon