with a rest arg, allow for keywords anywhere

with a rest arg, allow for keywords anywhere

* libguile/vm-i-system.c (br-if-nargs-gt): Fix variable declaration
  placement.
  (bind-kwargs): Patch mostly by Ludovic: it seems that in the mode in
  which we have rest args, the keywords can appear anywhere. Bummer.
  Change to allow for this.

* module/ice-9/optargs.scm (parse-lambda-case): Same, add a
  permissive-keys clause that handles the case in which there's a rest
  argument.