patch 8.0.0218: no completion for :cexpr and similar commands

Problem:    No command line completion for :cexpr, :cgetexpr, :caddexpr, etc.
Solution:   Make completion work. (Yegappan Lakshmanan)  Add a test.
diff --git a/src/version.c b/src/version.c
index 76b4350..2860968 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    218,
+/**/
     217,
 /**/
     216,