Define Float::INFINITY and Float::NAN if not already defined (< ruby 1.9)
Define Float::INFINITY and Float::NAN if not already defined (< ruby 1.9)

This paves the way for having inf, -inf, nan default values for
float/double fields.

localshred/protobuf,localshred/protobuf,brianstien/protobuf,ruby-protobuf/protobuf,film42/protobuf,lookout/protobuffy,zanker/protobuf,zanker/protobuf,lookout/protobuffy,film42/protobuf,quixoten/protobuf,brianstien/protobuf,quixoten/protobuf,ruby-protobuf/protobuf