warnings written to warning port

warnings written to warning port

* libguile/deprecation.c (scm_c_issue_deprecation_warning):
* libguile/load.c (auto_compile_catch_handler):
  (scm_sys_warn_auto_compilation_enabled, scm_primitive_load_path):
* module/ice-9/boot-9.scm (warn, %load-announce, duplicate-handlers)
  (load-in-vicinity):
* module/system/base/message.scm (warning): Write to the warning port.
  (*current-warning-port*): Alias the warning port.