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/Makefile b/src/Makefile
index 0dcf109..8de7104 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2150,6 +2150,7 @@
 	test_perl \
 	test_popup \
 	test_profile \
+	test_put \
 	test_quickfix \
 	test_regexp_latin \
 	test_regexp_utf8 \