* RUBY_INTERNAL_EVENT_NEWOBJ: object created.
* RUBY_INTERNAL_EVENT_FREE: object freeed.
* RUBY_INTERNAL_EVENT_GC_START: GC started.
  And rename `RUBY_EVENT_SWITCH' to `RUBY_INTERNAL_EVENT_SWITCH'.
  Internal events can not invoke any Ruby program because the tracing
  timing may be critical (under huge restriction).
  These events can be hooked only by C-extensions.
  We recommend to use rb_potponed_job_register() API to call Ruby
  program safely.
  This change is mostly written by Aman Gupta (tmm1).
  https://bugs.ruby-lang.org/issues/8107#note-12
  [Feature #8107]
* include/ruby/debug.h, vm_trace.c: added two new APIs.
* rb_tracearg_event_flag() returns rb_event_flag_t of this event.
* rb_tracearg_object() returns created/freeed object.
* ext/-test-/tracepoint/extconf.rb,
  ext/-test-/tracepoint/tracepoint.c,
  test/-ext-/tracepoint/test_tracepoint.rb: add a test.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40946 b2dd03c8-39d4-4d8f-98ff-823fe69b080e