Fix PGM syntax to comply with latest Arduino IDE (rev 1.5.7)

See: http://postwarrior.com/arduino-ethershield-error-prog_char-does-not-name-a-type/
Merge pull request #17 from flavio-fernandes/gaurav.master

Fix PGM syntax to comply with latest Arduino IDE (rev 1.5.7).
Tested for backwards-compatibility on 1.0.5