RFR: JDK-8183964: Bad lexing of javadoc comments (change in parsing/rendering of backslashes in javadoc)

[Jonathan Gibbons]

Please review this simple fix in the tokenizer for reading javadoc comments.
The fix is just to add a missing 'break' statement.

JBS: https://bugs.openjdk.java.net/browse/JDK-8183964
Webrev: http://cr.openjdk.java.net/~jjg/8183961/webrev.00

-- Jon