* libguile/goops.c (scm_c_extend_primitive_generic): Use
`SCM_SET_SUBR_GENERIC ()' instead of using `SCM_SUBR_GENERIC ()' as an
lvalue.
* libguile/procs.c (scm_c_make_subr_with_generic): Use `SCM_SET_SUBR_GENERIC_LOC ()'.
* libguile/procs.h (SCM_SET_SUBR_GENERIC, SCM_SET_SUBR_GENERIC_LOC): New macros.