patch 8.2.2606: strchars() defaults to counting composing characters

Problem:    strchars() defaults to counting composing characters.
Solution:   Add strcharlen() which ignores composing characters.
diff --git a/src/version.c b/src/version.c
index c5797c3..918a34c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2606,
+/**/
     2605,
 /**/
     2604,