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)

runtime/macros/matchit.vim

@@ -1,3 +1,5 @@
 " Load the matchit package.
 " For those users who were loading the matchit plugin from here.
-packadd matchit
+if 1
+    packadd matchit
+endif