Rebase throw/catch on top of raise-exception/with-exception-handler

* libguile/exceptions.c:
* libguile/exceptions.h: New files.
* libguile.h: Add exceptions.h.
* libguile/Makefile.am (libguile_@GUILE_EFFECTIVE_VERSION@_la_SOURCES):
  (DOT_X_FILES, DOT_DOC_FILES, modinclude_HEADERS): Add exceptions.c and
  exceptions.h.
* libguile/init.c (scm_i_init_guile): Initialize exceptions.
* libguile/threads.c (scm_spawn_thread): Use new names for
  scm_i_make_catch_handler and scm_c_make_thunk.
* libguile/throw.c: Rewrite to be implemented in terms of
  with-exception-handler / raise-exception.
* libguile/throw.h: Use data types from exceptions.h.  Move
  scm_report_stack_overflow and scm_report_out_of_memory to
  exceptions.[ch].
* module/ice-9/boot-9.scm (&error, &programming-error)
  (&non-continuable, make-exception-from-throw, raise-exception)
  (with-exception-handler): New top-level definitions.
  (throw, catch, with-throw-handler): Rewrite in terms of
  with-exception-handler and raise-exception.
: New top-level definitions.
* module/ice-9/exceptions.scm: Adapt to re-export &error,
  &programming-error, &non-continuable, raise-exception, and
  with-exception-handler from boot-9.
  (make-quit-exception, guile-quit-exception-converter): New exception
  converters.
  (make-exception-from-throw): Override core binding.
* test-suite/tests/eval.test ("inner trim with prompt tag"): Adapt to
  "with-exception-handler" being the procedure on the stack.
  ("outer trim with prompt tag"): Likewise.
* test-suite/tests/exceptions.test (throw-test): Use pass-if-equal.
* module/srfi/srfi-34.scm: Reimplement in terms of core exceptions, and
  make "guard" actually re-raise continuations with the original "raise"
  continuation.

libguile.h

@@ -49,6 +49,7 @@ extern "C" {
 #include "libguile/error.h"
 #include "libguile/eval.h"
 #include "libguile/evalext.h"
+#include "libguile/exceptions.h"
 #include "libguile/extensions.h"
 #include "libguile/fdes-finalizers.h"
 #include "libguile/feature.h"