Deprecate gc-live-object-stats

* libguile/gc.h:
* libguile/gc.c:
* libguile/deprecated.h:
* libguile/deprecated.c (scm_gc_live_object_stats): Deprecate; it hasn't
  worked in the whole 2.0 series.
Critical sections in guardians do not need to block asyncs

* libguile/guardians.c: Critical sections here cannot cause an
  async_tick, so they do not need to block asyncs.
GOOPS doc fix: #:dsupers is the init keyword for the dsupers slot.

* doc/ref/goops.texi (Metaclasses): #:dsupers is the initialization
  keyword for the dsupers slot, not #:supers.
Fix brainfuck->scheme compiler.

* module/language/brainfuck/compile-scheme.scm (compile-scheme): Fix
  brainfuck compiler.
Fix brainfuck comment

* module/language/brainfuck/parse.scm: Fix outdated comment.
vm: Gracefully handle stack overflows.

Fixes <http://lists.gnu.org/archive/html/guile-user/2013-12/msg00017.html>.
Reported by rvclayton@verizon.net (R. Clayton).

* libguile/vm.c (reinstate_stack_reserve): New function.
  (vm_error_stack_overflow): Install it as an unwind handler.
* test-suite/tests/control.test ("the-vm")["stack overflow reinstates
  stack reserve"]: New test.