small trick to get cleaner glsl code inside c/cpp files

[questor]

I just found this: https://emergent.unpythonic.net/01451504315 and think it's a really neat way to get cleaner shaders directly in cpp files... if it's not of interest to you just close this ticket.

[floooh]

Nice :) Shame about the "#version xxx\n" line though. The sapp-samples will soon be converted to the shader compiler where the shader code will be stashed away in a geneated header, but I'll consider it for the other backend-specific samples. I'll keep the ticket open as reminder.