patch 8.2.0559: clearing a struct is verbose

Problem:    Clearing a struct is verbose.
Solution:   Define and use CLEAR_FIELD() and CLEAR_POINTER().

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    559,
 /**/
     558,
 /**/