patch 8.0.0321: errors when trying to use scripts in tiny version

Problem:    When using the tiny version trying to load the matchit plugin
            gives an error. On MS-Windows some default mappings fail.
Solution:   Add a check if the command used is available. (Christian Brabandt)
diff --git a/src/version.c b/src/version.c
index 2d6940d..7a3d215 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    321,
+/**/
     320,
 /**/
     319,