RFR: JDK-8266779: Use <wbr> instead of ZERO_WIDTH_SPACE

[Hannes Wallnöfer]

This replaces usages of the zero-width space character (ZWSP, entity `​`) with the HTML5 `<wbr>` element. `<wbr>` acts as a word break opportunity without adding characters to the text content like ZWSP does. It is supported in all modern browsers, the only browser I  know of which doesn't support is are old versions of Internet Explorer. 

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/wbr
https://caniuse.com/wbr-element

I have tested the output (both layout and copy-paste behaviour) on Firefox, Safari, and Chrome on Mac OS X.

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Commit messages:
 - JDK-8266779: Use <wbr> instead of ZERO_WIDTH_SPACE

Changes: https://git.openjdk.java.net/jdk/pull/3946/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3946&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266779
  Stats: 374 lines in 25 files changed: 16 ins; 9 del; 349 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3946.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3946/head:pull/3946

PR: https://git.openjdk.java.net/jdk/pull/3946