RFR: 8184304: make tables in jdk.sctp module accessible

[Jonathan Gibbons]

Continuing the work to improve the accessibility and markup of our docs,
please review a small update to make the tables in the jdk.sctp module 
accessible.

JBS: https://bugs.openjdk.java.net/browse/JDK-8184304
Webrev: http://cr.openjdk.java.net/~jjg/8184304/webrev.00/index.html
API: http://cr.openjdk.java.net/~jjg/8184304/api.00/overview-summary.html

-- Jon