thread the module through syntax-case's expansion

thread the module through syntax-case's expansion

* libguile/debug.h:
* libguile/debug.c (scm_procedure_module): New procedure, returns the
  module that was current when the given procedure was defined. Used by
  syncase to scope free identifiers.

* module/ice-9/psyntax-pp.scm: Recompiled.

* module/ice-9/psyntax.scm: Thread the module through the syntax
  expansion. This is harder than it would appear because in many places
  the different components of syntax objects are destructured.

* module/ice-9/syncase.scm (guile-macro): Adapt to new signature for
  syntax transformer functions.