Problem: ":argadd" without argument is supposed to add the current buffer
name to the arglist.
Solution: Make it work as documented. (Coot, closesvim/vim#577)
2faa29f896
Problem: Using ":argadd" when there are no arguments results in the second
argument to be the current one. (Yegappan Lakshmanan)
Solution: Correct the w_arg_idx value.
a24f0a550f