8185994: Fix a11y and HTML issues in the java.base/java.io and java.base/java.nio packages
Reviewed-by: bpb, smarks

8181156: html5 issues in java.base javadoc
Reviewed-by: alanb

8133459: replace <tt> tags (obsolete in html5) in java.nio docs
Reviewed-by: lancea

8080901: Replace package.html files with package-info.java in the java.base module
Reviewed-by: lancea, alanb, vinnie