Add isDigit implementation to java.lang.Character

Signed-off-by: Ben Jackman <ben@jackman.biz>
Avoid use of deprecated ctor of IRTreePrinter
Merge pull request #960 from benjaminjackman/master

Add isDigit implementation to java.lang.Character
Merge pull request #961 from gzm0/no-deprecated

Avoid use of deprecated ctor of IRTreePrinter