thread_pthread.c: variable for errno

* thread_pthread.c (timer_thread_sleep): use a local variable for
  errno.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45898 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
thread.c: stop if forked in a sub-thread

* thread.c (thread_start_func_2): stop if forked in a sub-thread,
  the thread has become the main thread.
  [ruby-core:62070] [Bug #9751]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45899 b2dd03c8-39d4-4d8f-98ff-823fe69b080e