thread_pthread.c: fix compile error on HP-UX

* thread_pthread.c (sys/dyntune.h): for gettune().
* thread_pthread.c (hpux_attr_getstackaddr): fix missing *.
  [ruby-core:56983] [Feature #8793]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42808 b2dd03c8-39d4-4d8f-98ff-823fe69b080e