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.
diff --git a/src/version.c b/src/version.c
index 7275901..e6a7d8b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -790,6 +790,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    181,
+/**/
     180,
 /**/
     179,