[spline/bezier]Fix decoded buffer access violation.
Support flat shading.
[spline/bezier]Fix surface normal at flat shading.
Merge branch 'master' into spline_bezier
Fix flat shading for unsupported hardware.
Merge pull request #7115 from xebra/spline_bezier

spline/bezier fix and support flat shading
Merge https://github.com/hrydgard/ppsspp