RFR [9] 8133480: replace some tags (obsolete in html5) in core-libs docs

[Alexander Stepanov]

Hello,

Could you please review the following fix:
http://cr.openjdk.java.net/~avstepan/8133480/webrev.00
for
https://bugs.openjdk.java.net/browse/JDK-8133480

Just another portion of deprecated <tt> tags replaced with {@code }.
A single misprint was fixed; no other changes indicated by specdiff.

Thanks,
Alexander