Sorry SdFat no longer compiles for the Sanguino. The official software for the Sanguino is so out of date, 0018, that I have given up testing with Sanguino.
I have left the 644/644P ifdefs in the SdFat code.
Since SdFat is the base for the "native SD library" it will also break for the Sanguino if the Arduino group updates to the new version of SdFat.