vim-patch:6a598be test for 7.4.487

https://code.google.com/p/vim/source/detail?r=6a598be6d4e8
vim-patch:7.4.487

Problem:    ":sign jump" may use another window even though the file is
	    already edited in the current window.
Solution:   First check if the file is in the current window. (James McCoy)

https://code.google.com/p/vim/source/detail?r=v7-4-487