CompactFormatter precision and surrogate pairs

[jmehrens]

Working on improving the code coverage for the CompactFormatter I noticed that the logic for handling precision can bisect a supplementary character.

The faulty code is here:
https://github.com/eclipse-ee4j/mail/blob/226d2d6f1db283042537fa9a30dfab798649fea2/mail/src/main/java/com/sun/mail/util/logging/CompactFormatter.java#L812

In its current form, the code is just dead code that could produce a garbage character. The good news is that java.util.Formatter doesn't handle supplementary characters either. See: java.util.Fomatter precision and surrogate pairs. This means that for all argument indexes precision will bisect in the same manor. Since the default format is using CompactFormatter$Alternate with a precision, supplementary characters should be handled correctly.

Need to write up tests to ensure that all CompactFormatter$Alternate parameters don't bisect supplementary characters.
In general the change is roughly:

• Initial fence needs to be determined by counting code points.
• Change the if to less than (or less than equal)
• The substring should be incremented to the right instead of the left.
• The fence shouldn't change because even though the string is larger it didn't take away any code points from the right side.
• The right side string needs all of the same checking for supplementary characters the end of string.
• Need to deal with not moving if the next char isn't the low surrogate.
• Add tests for all of the possible bounds issues and edge cases.
• Update JavaDocs to talk about precision is in code points.

[jmehrens]

Committed to 2.0.2-SNAPSHOT and 1.6.7-SNAPSHOT