Rename $ktrunc to $kreceive

Rename $ktrunc to $kreceive

* module/language/cps.scm ($kreceive): Rename from ktrunc.

* module/language/cps/arities.scm:
* module/language/cps/compile-bytecode.scm:
* module/language/cps/dce.scm:
* module/language/cps/dfg.scm:
* module/language/cps/effects-analysis.scm:
* module/language/cps/elide-values.scm:
* module/language/cps/simplify.scm:
* module/language/cps/slot-allocation.scm:
* module/language/cps/verify.scm:
* module/language/tree-il/compile-cps.scm: Adapt all users.