RFR: JDK-8215210: [macos] Hangul text does not shape to the precomposed form on JDK8u

[Yuri Nesterenko]

Hi all,

could you please review this downport of
https://bugs.openjdk.java.net/browse/JDK-8215210 to openjdk 8u?

Link to webrev: http://cr.openjdk.java.net/~yan/8215210/webrev.0/

There is a single digit change discovered by prr and a couple of
regression tests:

one verifies that required shaping works as expected and another -- that
there's no obvious regression for JDK-8201801
<https://bugs.openjdk.java.net/browse/JDK-8201801>

Thank you!

--yan