Fixed JSSC upload problem with Arduino Due on MacOSX

JSSC, on unix based systems like linux and MacOSX, when listing serial ports
tries to open each port to ensure its existence. While this check works well for
linux ports /dev/ttyS0..31, it leads to unexpected behaviuors on MacOSX in
particular with USB-CDC virtual serial ports.
This patch disable the check and keep it enabled only for linux ttySxx ports.

This adds also tty.* and cu.* to the list of available serial ports on MacOSX.