patch 8.1.1404: cannot change the patch level when building with NSIS

Problem:    Cannot change the patch level when building with NSIS.
Solution:   Use $PATCHLEVEL if defined. (Christian Brabandt)
diff --git a/src/version.c b/src/version.c
index 4dbff0b..2b869f0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1404,
+/**/
     1403,
 /**/
     1402,