RFR [9] 8133459: replace <tt> tags (obsolete in html5) in java.nio docs

Hello, Could you please review the following fix: http://cr.openjdk.java.net/~avstepan/8133459/webrev.00/index.html for https://bugs.openjdk.java.net/browse/JDK-8133459 Just a next portion of deprecated '<tt>' tags replaced (didn't touch all these multiple ' 's to avoid undesirable formatting changes). specdiff did not detect any changes in java.nio.* Regards, Alexander