Use allocate-struct in define-record-type implementations

Use allocate-struct in define-record-type implementations

* module/ice-9/boot-9.scm (iota): Move up.
  (make-record-type, define-record-type): Use allocate-struct and
  struct-set!.

* module/srfi/srfi-9.scm (%%set-fields, %define-record-type): Use
  allocate-struct and struct-set!.

Note that this makes the stack VM slower, but it will make RTL
compilation faster.