patch 8.1.0387: no test for 'ambiwidth' detection

Problem:    No test for 'ambiwidth' detection.
Solution:   Add a test.
diff --git a/src/version.c b/src/version.c
index 81fc685..9b2e81b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    387,
+/**/
     386,
 /**/
     385,