I found that a fix posted in the Repetier forum also works in Marlin
I was compiling Marlin 1.1.x on Arduino 1.8.2 for RAMBo 1.2d
I got this error:
'DIGIPOT_MOTOR_CURRENT' was not declared in this scope
I uncommented the line below in Marlin's Configuration_adv.h
#define DIGIPOT_MOTOR_CURRENT { 135,135,135,135,135 } // Values 0-255 (RAMBO 135 = ~0.75A, 185 = ~1A)
...and it compiles fine.