vim-patch:8.1.2375: no suffucient testing for registers

Problem:    No suffucient testing for registers.
Solution:   Add more test cases. (Yegappan Lakshmanan, closes vim/vim#5296)
            Fix that "p" on last virtual column of tab inserts spaces.
6f1f0ca3ed

This patch doesn't actually change any behavior in Nvim, because Nvim
always has vartabs feature.

I modified a line in the test because of #6137.

src/nvim/testdir/test_visual.vim

@@ -433,6 +433,19 @@ func Test_Visual_Block()
   close!
 endfunc
 
+" Test for 'p'ut in visual block mode
+func Test_visual_block_put()
+  enew
+
+  call append(0, ['One', 'Two', 'Three'])
+  normal gg
+  yank
+  call feedkeys("jl\<C-V>ljp", 'xt')
+  call assert_equal(['One', 'T', 'Tee', 'One', ''], getline(1, '$'))
+
+  enew!
+endfunc
+
 func Test_visual_put_in_block()
   new
   call setline(1, ['xxxx', 'y∞yy', 'zzzz'])