vm.c: remove rb_vm_living_threads_foreach function

Shorter code with fewer callbacks and casts should be more readable.

* vm.c (rb_vm_living_threads_foreach): remove function
  [ruby-core:62745]
* thread.c (terminate_i): remove
* thread.c (terminate_all): implement (inlines old terminate_i)
* thread.c (rb_thread_terminate_all): use terminate_all
* thread.c (rb_thread_fd_close_i): remove
* thread.c (rb_thread_fd_close): iterate inline
* thread.c (thread_list_i): remove
* thread.c (rb_thread_list): iterate inline
* thread.c (rb_thread_atfork_internal): iterate inline
* thread.c (terminate_atfork_i): update types to remove casts
* thread.c (terminate_atfork_before_exec_i): ditto
* thread.c (struct thgroup_list_params): remove definition
* thread.c (thgroup_list_i): remove
* thread.c (thgroup_list): iterate inline
* thread.c (check_deadlock_i): remove
* thread.c (debug_deadlock_check): implement (inlines check_deadlock_i)
* thread.c (debug_i): remove
* thread.c (rb_check_deadlock): iterate inline
* vm.c (vm_mark_each_thread_func): remove
* vm.c (rb_vm_mark): iterate inline
* vm_core.h (rb_vm_living_threads_remove): remove
* vm_trace.c (clear_trace_func_i): remove
* vm_trace.c (rb_clear_trace_func): iterate inline

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46195 b2dd03c8-39d4-4d8f-98ff-823fe69b080e