Release Note: Support Supplementary Characters in String Case Insensitive Operations

Case insensitive operations in `java.lang.String` class now correctly do case insensitive comparisons for supplementary characters (characters which have code point values over `U+FFFF`). For details, see the updates to the methods:
```
   - compareToIgnoreCase(String other)
   - equalsIgnoreCase(String other)
   - regionMatches(boolean ignoreCase, ...)
```
For example,
```
"\ud801\udc00".equalsIgnoreCase("\ud801\udc28")
```
returns `true`, because '𐐀' ("\ud801\udc00") and '𐐨' ("\ud801\udc28") are equal to each other character in case insensitive comparison.