Testing how to implement shader macros in cepl.
This and shader compile callbacks will make things very slick, as
it will feel just like lisp.
And now we have macros
replace-nth function added to utils
Merge branch 'shader-macros'

Conflicts:
	examples/2.lisp
* Fixed bug in defpipeline. Only the first line of multiline in-place
  shader stage definitions were compiled.
* working on exampel 12, currently not working