Add Java 6's java.net.IDN.

harmony's tests and my code, though ICU4C does all the hard work.

I've added a test of my own to demonstrate some weird RI behavior (that I've
emulated in our implementation).

Bug: 2497395
Change-Id: I8146f72a8a3204449ee3d0d9065dadc1c1c77fcc
1 file changed