Redundant Validity Checks in Flood Fill Julia and C Implementations

[lazyprop]

In the Julia and C implementations, the color function checks if the point is inside bounds and if old_val == new_val.
These conditions are already checked in the find_neighbours function. So the points which are passed to color will always satisfy these conditions.The conditions are totally unnecessary.
color can simply be:

def color(canvas, p, new_val):
    canvas[p] = new_val

[lazyprop]

#752, and #743 have the same problem.

[lazyprop]

I think this issue has been fixed in all the implementations. I will close this now.