RFR: [15] JDK-8247788 DocCommentParser should not reject standalone '>'

[Jonathan Gibbons]

Please review a small change to remove an inappropriate restriction on
the use of '>' in HTML text.  There is no such restriction in HTML 5, and
it seems the same was true for HTML 4.

The check, the error message and an example for the diagnostic are all 
removed.

A negative test case in ElementTest.java is converted into a positive 
test case,
and the bug attached to that test.  Some other tests needed to be updated.

-- Jon

JBS: https://bugs.openjdk.java.net/browse/JDK-8247788
Webrev: http://cr.openjdk.java.net/~jjg/8247788/webrev.00/