Ruby

merges r21659 from trunk into ruby_1_9_1.

• vm.c: add a prefix "rb_" to exposed functions
  vm_get_ruby_level_next_cfp(), rb_vm_make_env_object(),
  vm_stack_to_heap(), vm_make_proc(), vm_invoke_proc(),
  vm_get_sourceline(), vm_cref(), vm_localjump_error(),
  vm_make_jump_tag_but_local_jump(), vm_jump_tag_but_local_jump().
  This changes may affect only core because most of renamed functions
  require a pointer of not-exposed struct such as rb_thread_t or NODE.
  In short, they are core functions.
• cont.c, eval.c, eval_intern.h, load.c, proc.c, thread.c,
  vm_core.h, vm_dump.c, vm_eval.c, vm_exec.c, vm_insnhelper.c:
  ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@21849 b2dd03c8-39d4-4d8f-98ff-823fe69b080e