Fill bucket: Use a more accurate algorithm

Steps to reproduce:

• open Inkscape
• draw a closed shape
• zoom out as far as practical
• fill the shape
• get back to a normal zoom level
• draw another closed shape
• zoom in so the shape extends over the edges of the "viewport"
• try to fill the shape, observe how the message "Area not bounded, cannot fill" is shown
• zoom out so the shape is a large as possible whil still being visible in its entirety
• fill the shape

What happened?

fills at low zoom levels are not consistent with those at higher zoom values. filling a closed shape that is not entirely visible results in no fill at all.

filling a large, complex shape is made impossible because low zoom levels are required to see the shape in its entirety, while high zoom levels are required for a detailed fill.

What should have happened?

filling shapes should be consistent whatever the zoom value is. filling should extend over the edges of the viewport (OR the viewport's edges should act as a bounding box if filling the whole shape is exceedingly hard)

Inkscape Version and Operating System:

• Inkscape Version: 1.0 beta
• Operating System: all
• Operating System any