Disallow creating a degenerate line segment

[itzpr3d4t0r]

Right now we allow having a "point" line segment:

line = Line(1, 1, 1, 1)

This has to be fixed. many times we divide by x2-x1 or y2-y1 and that will error out.
My idea is to implement a new check function to add inside the pgLine_FromObject function after the line attributes are set that checks their validity. if not it will error out.