clear buffer-local BufWinEnter properly
clear buffer-local BufWinEnter properly

Fix the check for a buffer-local BufWinEnter autocmd in
go#guru#ClearSameIds() so that multiple BufWinEnter autocmds are not
registered to rehighlight the sameids when re-entering the local buffer.

andviro/vim-go,andviro/vim-go