Problem: hard to get visual region using Vim script
Solution: Add getregion() Vim script function
(Shougo Matsushita, Jakub Łuczyński)
closes: vim/vim#13998closes: vim/vim#115793f905ab3c4
Cherry-pick changes from patch 9.1.0122, with :echom instead of :echow.
Co-authored-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Co-authored-by: Jakub Łuczyński <doubleloop@o2.pl>