RFR: Update tables in java.base to be HTML5-friendly.

[Jonathan Gibbons]

This is a review request for two co-dependent fixes.

JDK-8179592: Update tables in java.base to be HTML 5-friendly.
JDK-8179479: Add new styles to enable HTML 5 tables

In doc comments, some of the HTML 4.01 attributes for tables are no 
longer available in HTML 5, and CSS should be used instead.
To this end, some updates have been made to the main/default stylesheet 
used by javadoc, to define two new CSS classes for tables.

The new classes are:
     <table class="plain">
     Just puts plain borders around each cell, with no background coloring.

     <table class="altrows">
     Horizontal borders are not used between cells in the table body; 
instead, alternating backgrounds are used to help distinguish the 
separate rows.

In addition, there is still the default
     <table>
     No borders.

These styles are in the langtools webrev, here:
     http://cr.openjdk.java.net/~jjg/8179479-8179592/8179479/webrev/

The changes to the doc comments in java.base are in the jdk webrev, here:
     http://cr.openjdk.java.net/~jjg/8179479-8179592/8179592/webrev/

summary vs. <caption>

    The ARIA recommendations are to use the summary attribute or 
<caption> tag ... but the summary attribute is no longer allowed in HTML 
5.  In general, the text that has been provided for a summary is not 
suitable for direct use as a caption. The temporary workaround is to use 
a caption that is not displayed. In time, the appropriate API owners 
should update the use of these undisplayed table captions, to modify the 
text of the caption and make the caption displayed (by removing 
style="display:none").

Doc comments were changed in files in the following packages:

java.io
java.lang
java.lang.invoke
java.lang.reflect
java.math
java.net
java.nio.channels
java.nio.charset
java.nio.file
java.nio.file.attribute
java.nio.file.spi
java.security
java.security.cert
java.text
java.time.chrono
java.time.format
java.time.temporal
java.util
java.util.concurrent
java.util.regex
java.util.spi
javax.net.ssl

The intent is that the only changes in this webrev are to the HTML 5 
markup. There should be no significant changes to the text in any doc 
comment.

The decision to add the styles to the default stylesheet at this late 
stage in the release is not taken lightly, and is seen as a temporary 
measure. JDK-8177283 is a wishlist enhancement for updates to javadoc 
support of stylesheets, which includes the desire to move JDK-specific 
styles to a JDK-specific stylesheet.

This review is primarily about continuing the ongoing effort to make our 
docs be HTML 5 compliant. I would prefer not to get into extended 
discussions about which style class to use for each table, and what the 
exact definition of the styleclasses should be at this time.  But 
appropriate review feedback is obviously welcome.

-- Jon