Add a way to print debug counters without exiting

I am trying to study debug counters inside a Rails application.
Accessing debug counters by killing the process is hard because child
processes don't get the same TRAP as the parent, and Rails seems to
intercept calls to `exit`.  Adding this method lets me print the debug
counters when I want (at the end of requests for example)

1 files changed, 1 insertions, 0 deletions

diff --git a/vm.c b/vm.c
index b4e2e3c5e6..a0a04c6337 100644
--- a/vm.c
+++ b/vm.c
@@ -2916,6 +2916,7 @@ Init_VM(void)
     rb_define_singleton_method(rb_cRubyVM, "stat", vm_stat, -1);
 #if USE_DEBUG_COUNTER
     rb_define_singleton_method(rb_cRubyVM, "reset_debug_counters", rb_debug_counter_reset, 0);
+    rb_define_singleton_method(rb_cRubyVM, "show_debug_counters", rb_debug_counter_show, 0);
 #endif
 
     /* FrozenCore (hidden) */