merge revision(s) 39766,39769: [Backport #8101]

	* time.c (GetTimeval): check if already initialized instance.

	* time.c (GetNewTimeval): check if newly created instance.

	* time.c (time_init_0, time_init_1, time_init_copy, time_mload): must
	  be newly created instance.  [ruby-core:53436] [Bug #8099]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40282 b2dd03c8-39d4-4d8f-98ff-823fe69b080e