Save some cycle inside the planner

planner.h:
fan speed is used to set integer variables, so no need for long.
Basicaly a byte should be enough for all the fan things, as it's 0-255?

planner.cpp:
Save some float multiplications.
We could squeeze out even more by defining feedrate_percentage,
saved_feedrate_percentage and flow_percentage as float instead of int.
Everytime they are used in the time-critical planner, they are casted to
float and multiplied by 0.01. Not done jet, as they are used in LCD menu
functions I don't know well enough.