Better aliased primcall compilation

Better aliased primcall compilation

* libguile/vm-engine.c (define!): Rename from define.
* module/language/cps/arities.scm (fix-clause-arities): If a prim
  aliases an RTL instruction with a different name and we reify a
  primcall, reify the instruction name.
* module/language/cps/compile-rtl.scm (emit-rtl-sequence): Update
  emit-define! for new name.
* module/language/cps/primitives.scm (*rtl-instruction-aliases*): Add
  bytevector native accessors.