* libguile/continuations-internal.h: New file, for internal definitions.
* libguile/continuations.h: Move out internal definitions.
* libguile/Makefile.am: Add new file.
* libguile/continuations.c: Adapt to put the tag in the beginning of the
continuation (contregs) structure.
* libguile/eq.c:
* libguile/goops.c:
* libguile/init.c:
* libguile/print.c:
* libguile/scm.h:
* libguile/stacks.c:
* libguile/vm.c:
* module/oop/goops.scm: Adapt to contregs tc16 change.
