patch 8.0.0222: blockwise put on multi-byte character misplaced

Problem:    When a multi-byte character ends in a zero byte, putting blockwise
            text puts it before the character instead of after it.
Solution:   Use int instead of char for the character under the cursor.
            (Luchr, closes #1403)  Add a test.
diff --git a/src/testdir/test_alot.vim b/src/testdir/test_alot.vim
index 9a7c35d..2b163ae 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -31,6 +31,7 @@
 source test_messages.vim
 source test_partial.vim
 source test_popup.vim
+source test_put.vim
 source test_reltime.vim
 source test_searchpos.vim
 source test_set.vim