* thread_pthread.c (USE_SLEEPY_TIMER_THREAD): use more accurate
ifdef condtions.
* thread_pthread.c (timer_thread_sleep): use poll() instead of
select(). select doesn't work if timer_thread_pipe[0] is
greater than FD_SETSIZE.
* thread_pthread.c (USE_SLEEPY_TIMER_THREAD): add a dependency
against poll.
merge revision(s) 39680,39681: [Backport #8063]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39726 b2dd03c8-39d4-4d8f-98ff-823fe69b080e