Mac OS X sends a SCSI command to remove the medium when it unmounts a
drive. If this command is not honoured, then OS X will automatically
remount the drive, making it impossible to eject. This patch disables
the USB MSC when the right SCSI command is sent.
All board config macros now begin with MICROPY_HW_.
Renamed PYBv10 to PYBV10, since macros should be all uppercase.
Made SDCARD_DETECT configurable in mpconfigport.h, so that the SD
detect pin can be easily configured.
Damien George