add `formals', `body', and `compile-env' slots to <method>

add `formals', `body', and `compile-env' slots to <method>

* ice-9/boot-9.scm (compile-time-environment): Return #f instead of
  erroring under the interpreter, a bit more sane.

* libguile/goops.c (create_standard_classes):
* libguile/goops.h (scm_si_formals, scm_si_body, scm_si_compile_env):
* oop/goops.scm (method, initialize): Add `formals', `body', and
  `compile-env' slots to <method>.