merge revision(s) 40163: [Backport #8228]

	* configure.in (AC_CHECK_HEADERS): atomic.h for Solaris atomic_ops.

	* ruby_atomic.h: Skip using Solaris10 atomic_ops on Solaris 9 or
	  earlier if atomic.h is not available. [ruby-dev:47229] [Bug #8228]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40285 b2dd03c8-39d4-4d8f-98ff-823fe69b080e