patch 8.1.0181: memory leak with trailing characters in skip expression

Problem:    Memory leak with trailing characters in skip expression.
Solution:   Free the return value.

src/version.c

@@ -789,6 +789,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    181,
 /**/
     180,
 /**/