Flatten Beziers: raise lower limit for flatness factor to prevent endless loop in python script

[su_v]

Steps to reproduce:
1) launch inkscape
2) draw a curve
3) open 'Extensions > Modify Path > Flatten Beziers'
4) set flatness to 0.0
5) apply

--> the python process is endlessly processing the path with 100% CPU, and never returns control to the main Inkscape process.

Proposed solution:
Raise lower limit in the INX file from '0.0' to '0.1' for the flatness factor.

Additional proposed change:
Move setting the final path data outside the inner loop (AFAICT there's no need to reformat and write 'd' for each step).

[Hachmann (marenhachmann)]

Thank you for investigating and fixing! :D

[jazzynico (jazzynico)]

Fix (and performance improvement...) tested successfully on Xubuntu 15.04 with Inkscape trunk rev. 14380.
Feel free to commit!

[su_v (suv-lp)]

@JazzyNico - thanks for testing!

Fix committed to trunk in rev 14381,
backported to lp:inkscape/0.91.x in rev 13786.