todo

* why use def-v-type-class for v-user-function? Switch to defclass?

* low-hanging-fruit: unify labels/flet/labels-no-implicit implementations

* need an across vector loop thing. We can then unroll these loops.
* also add all the arithmatic operators for non number datatypes
* add aref, make-array and array constructors

* add-function to global should remove functiosn that are totally blocked, so match
  on (cons func-name (v-args func)) as only the newsest one will be selected and it slows
  down processing
* merge-obs needs a new name
* Write tour guide

* read up on setting variables as invariant
* find out what centroid means
* add preprocessor extensions to translate function
* check out _line_ _file_ and _version_ macros from glsl, are they
  used?
* add lisp macros wrappers for this functionality
* add constants
* how do we handle ARBs?