gc.c: flush all deferred finalizers

* gc.c (finalize_deferred): flush all deferred finalizers while other
  finalizers can get ready to run newly by lazy sweep.
  [ruby-core:58833] [Bug #9205]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43994 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
ruby_atomic.h: duplicate code

* ruby_atomic.h (ATOMIC_SIZE_CAS): remove duplicate code as
  ATOMIC_CAS().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43995 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
ruby_atomic.h: ATOMIC_PTR_EXCHANGE

* ruby_atomic.h (ATOMIC_PTR_EXCHANGE): atomic exchange function for
  a generic pointer.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43996 b2dd03c8-39d4-4d8f-98ff-823fe69b080e