Arm doesn't have PROGMEM. In theory, the DUE ide should have defined all the PROGMEM 'keywords' as nothing and all of the _P functions as , but maybe they missed a few places.
If you are only programming on the Due, and no longer target the AVR based microprocessors, just take out the PROGMEM stuff. If you need to run on both platforms, then you probably should do something like:
#if defined(__arm__) && !defined(PROGMEM)
#define PROGMEM
#define PSTR(STR) STR
#endif
You probably need more than that, depending on your program.