patch 8.1.0642: swapinfo() leaks memory

Problem:    swapinfo() leaks memory.
Solution:   Avoid allocating the strings twice.
diff --git a/src/version.c b/src/version.c
index 3150da9..dc11358 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    642,
+/**/
     641,
 /**/
     640,