deprecate arity access via (procedure-properties proc 'arity)

deprecate arity access via (procedure-properties proc 'arity)

* libguile/procprop.h (scm_sym_arity): Deprecate. I didn't move it to
  deprecated.h though, because that might have some boot implications --
  though I didn't check.

* libguile/procprop.c (scm_procedure_properties)
  (scm_set_procedure_properties_x, scm_procedure_property)
  (scm_set_procedure_property_x): Deprecate access to a procedure's
  arity via procedure-properties. Users should use
  procedure-minimum-arity.

* module/ice-9/channel.scm (eval):
* module/ice-9/session.scm (arity):
* module/language/tree-il/analyze.scm (validate-arity): Fix up instances
  of (procedure-property x 'arity) to use procedure-minimum-arity.