merge revision(s) 39372,39383: [Backport #7912]

	* test/test_rbconfig.rb (TestRbConfig): skip user defined values by
	  configuration options.  [Bug #7902]

	* test/test_rbconfig.rb (TestRbConfig): fix r39372.
	  It must see RbConfig::CONFIG instead of CONFIG.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39661 b2dd03c8-39d4-4d8f-98ff-823fe69b080e