patch 8.2.0799: build fails if snprintf is not available

Problem:    Build fails if snprintf is not available.
Solution:   Use vim_snprintf().
diff --git a/src/version.c b/src/version.c
index 4c3cab7..f79ad75 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    799,
+/**/
     798,
 /**/
     797,