Features have been added to support an unmodified Adafruit GPS Shield
or Datalogging Shield on an Arduino Mega.

Define MEGA_SOFT_SPI to be non-zero in SdFatConfig.h to use software SPI 
on Mega Arduinos.  Pins used are SS 10, MOSI 11, MISO 12, and SCK 13.

Defining MEGA_SOFT_SPI allows an unmodified Adafruit GPS Shield to be
used on Mega Arduinos.  Software SPI works well with GPS Shield V1.1
but many SD cards will fail with GPS Shield V1.0.

Software SPI should work with all Datalogging Shields.

The examples SdFatGPS_CSVSensorLogger.pde and SdFatGPSLogger_v3.pde
should work on on the Mega when MEGA_SOFT_SPI is defined.