Change data type of step() parameter to `long`

[lagabulin]

Hello.
My Arduino Uno board cannot handle steps_to_move bigger than 32767 which is the maximum of 16bits integer.
This was simply solved by modifying the int in below two lines to long.
I would like to modify the parts below so that we can use a wider range of step numbers without changing the board.
Is there any reason that we have to use int datatype instead of long datatype?

Stepper/src/Stepper.cpp

Line 184 in 9189fa7

void Stepper::step(int steps_to_move)

Stepper/src/Stepper.cpp

Line 186 in 9189fa7

int steps_left = abs(steps_to_move); // how many steps to take