Add new test file.

src/testdir/test_visual.vim

@@ -0,0 +1,19 @@
+" Tests for Visual mode
+if !has('multi_byte')
+  finish
+endif
+set encoding=utf-8
+scriptencoding utf-8
+
+if !has('visual')
+  finish
+endif
+
+func Test_block_shift_multibyte()
+  split
+  call setline(1, ['xヹxxx', 'ヹxxx'])
+  exe "normal 1G0l\<C-V>jl>"
+  call assert_equal('x	 ヹxxx', getline(1))
+  call assert_equal('	ヹxxx', getline(2))
+  q!
+endfunc