merge revision(s) 42040,42041,42047: [Backport #8654]

	* array.c (rb_ary_count): iterate items appropriately.
	  [Bug #8654]

	* array.c (rb_ary_count): check length to avoid SEGV
	  while iterating. Remove other pointer loop when arg is given.

	* test/ruby/test_array.rb (test_count): add test for bug.
	  [ruby-core:56072] [Bug #8654]

	* test/ruby/test_array.rb (test_count): add a test case for #count
	  with an argument. See Bug #8654.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@43228 b2dd03c8-39d4-4d8f-98ff-823fe69b080e