patch 8.1.0008: no test for strwidth()

Problem:    No test for strwidth().
Solution:   Add a test. (Dominique Pelle, closes #2931)
diff --git a/src/version.c b/src/version.c
index f18e711..f2fa2a7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    8,
+/**/
     7,
 /**/
     6,