Ruby » Ruby master

• vm_core.h (rb_thread_struct): added 'in_trap' member for marking
  running trap handler.
• signal.c (signal_exec): turn on in_trap when running trap.
• thread.c (Init_Thread, thread_create_core): initialize in_trap
  when creating new threads.
• thread.c (thread_join_m): raise ThreadError when running trap
  handler.Bug [#6416][ruby-core:44956]
• test/ruby/test_thread.rb (test_thread_join_in_trap): new test
  for the above.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37852 b2dd03c8-39d4-4d8f-98ff-823fe69b080e