patch 8.2.3320: some local functions are not static

Problem:    Some local functions are not static.
Solution:   Add "static".  Move snprintf() related code to strings.c.
            (Yegappan Lakshmanan, closes #8734)
diff --git a/src/window.c b/src/window.c
index 1cc8549..b0bdd59 100644
--- a/src/window.c
+++ b/src/window.c
@@ -4475,7 +4475,7 @@
 #endif
 }
 
-#if defined(FEAT_PERL) || defined(FEAT_LUA) || defined(PROTO)
+#if defined(FEAT_PERL) || defined(PROTO)
 /*
  * Find window number "winnr" (counting top to bottom).
  */