Problem: Cannot get the script line number when executing a function.
Solution: Store the line number besides the script ID. (Ozaki Kiichi,
closesvim/vim#3362) Also display the line number with ":verbose set".
f29c1c6aa3
Problem: maparg() and mapcheck() confuse empty and non-existing.
Solution: Return <Nop> for an existing non-empty mapping. (closesvim/vim#2940)
f88a5bc102