Apply clang format as proposed in T53211.
For details on usage and instructions for migrating branches
without conflicts, see:
https://wiki.blender.org/wiki/Tools/ClangFormat
These are intended for very simple drawing. No lighting etc.
Shares some fragment code with the 2D shaders.
Similar to their 2D counterparts, but are not combined because of
future plans for separate 2D & 3D matrix stacks.