Change Show instances for Char and String to match their literals
Adjust tests to the changed String show instance
Fix Char literal matching in C codegen
Update language-java dependency to 0.2.6

This version is required for the Java backend to emit correct char and string
literals in nonprinting and/or nonascii cases.
Fix rendering of LChInt in Java backend
Merge pull request #669 from Melvar/showstring

Change Show instances for Char and String to match their literals