RFR: JDK-8287674: CSS improvements for summary lists [v4]

[Hannes Wallnöfer]

> This is a refinement of CSS styles mostly in the deprecated and new API pages.
> 
>  - Provide a two-row table view for the new sortable three-column tables
>  - Make sure no line wraps are inserted between a checkbox and its label
>  - Slightly increase the line height of the check box row to make it easier to use when wrapped
>  - Define the overflow of summary table cells as "auto" which makes them scrollable if necessary

Hannes Wallnöfer has updated the pull request incrementally with two additional commits since the last revision:

 - Remove unused imports
 - Use normal space instead of <wbr> as the latter is not rendered as space by Chrome

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8975/files
  - new: https://git.openjdk.java.net/jdk/pull/8975/files/2bed76c1..7ae1fc73

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8975&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8975&range=02-03

  Stats: 16 lines in 3 files changed: 0 ins; 2 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8975.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8975/head:pull/8975

PR: https://git.openjdk.java.net/jdk/pull/8975