patch 8.0.0446: the ";" command does not work after some characters

Problem:    The ";" command does not work after characters with a lower byte
            that is NUL.
Solution:   Properly check for not having a previous character. (Hirohito
            Higashi)
diff --git a/src/Makefile b/src/Makefile
index 0238836..1af1e17 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2099,6 +2099,7 @@
 	test_cdo \
 	test_channel \
 	test_charsearch \
+	test_charsearch_utf8 \
 	test_changedtick \
 	test_cindent \
 	test_cmdline \