* debug.c (ruby_debug_print_indent): returns if debug_level exceeds
  the threashold.

* debug.c (ruby_debug_printf): printf to stderr.

* iseq.c (make_compile_option, make_compile_option_value): added
  debug_level option.

* vm_core.h (rb_compile_option_t): added debug_level.

* vm_core.h (struct iseq_compile_data): added node_level.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@16003 b2dd03c8-39d4-4d8f-98ff-823fe69b080e