Extend the 1.9 Sprinter to handle negative numbers in hex, octal, binary

Correctly append ".." in front of negative integers when they are
formatted into hex, octal or binary (%x, %X, %o, %b).

Also remove dead code and pointless predicate methods that simply
delegate to ivars.
Merge pull request #2263 from leocassarani/sprinter-negative-int

Extend the 1.9 Sprinter to handle negative numbers in hex, octal, binary