Blender Git Loki

Changes in double side lighting usage

Disabled double-side lighting by default and changed areas which are using
double sided lighting to switch it off just after doing stuff which requires
double side.

This makes code a bit more simple to follow (no all that disabling double side
lighting all over the code and so).

This change also fixes crash of blender caused by intel gme965 driver which
leads to stack corruption in some place when double side lighting isn't
disabled (probably driver still kind of using double side in some areas or so).

Hopefully it'll also fix #30293: Converting Text to Mesh

Thanks to Campbell to assist writing this patch!