New feature:

Automatic switching for drawing pixel buffers via glDrawPixels or using GPU textures

It works with a User Preference limit, in megapixels, to define whether to use
GPU or direct pixel drawing. Default is now initialized to 10 MP (4k buffers).

Especially for zooming out (draw smaller) texture drawing is much smaller. Also
Nvidia cards typically draw much faster with textures in general.

Added to node backdrop first now, the other editors follow in a next commit.

For coders: added new DNA function to initialize new struct variables, so you
don't have to sub-version files anymore.

   DNA_struct_elem_find(fd->filesdna, "structname", "typename", "varname") 

"filesdna" is the sdna description of the current file being versioned.





git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55354 954f8c5b-7b00-dc11-b283-0030488c597c