merge revision(s) 39810: [Backport #8145]

	* gc.c: Fix unlimited memory growth with large values of
	  RUBY_FREE_MIN. patched by tmm1(Aman Gupta).
	  [Bug #8095] [ruby-core:53405]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40177 b2dd03c8-39d4-4d8f-98ff-823fe69b080e