merge revision(s) 34278:

	* cont.c (cont_restore_0): prevent optimizing out `sp'. sp is used for
	  reserving a memory space with ALLOCA_N for restoring machine stack
	  stored in cont->machine_stack, but clang optimized out it (and
	  maybe #5851 is also caused by this).
	  This affected TestContinuation#test_check_localvars.

	* cont.c (cont_restore_1): revert workaround introduced in r32201.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_2@40303 b2dd03c8-39d4-4d8f-98ff-823fe69b080e