patch 8.2.0903: comparing WINVER does not work correctly

Problem:    comparing WINVER does not work correctly.
Solution:   Use arithmethic expansion. (Ozaki Kiichi, closes #6197)
diff --git a/src/version.c b/src/version.c
index bb18367..399886e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    903,
+/**/
     902,
 /**/
     901,