patch 8.2.0514: several global functions are used in only one file

Problem:    Several global functions are used in only one file.
Solution:   Make the functions static. (Yegappan Lakshmanan, closes #5884)
diff --git a/src/evalvars.c b/src/evalvars.c
index c4bc957..d434d58 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -2435,7 +2435,7 @@
 /*
  * Get the script-local hashtab.  NULL if not in a script context.
  */
-    hashtab_T *
+    static hashtab_T *
 get_script_local_ht(void)
 {
     scid_T sid = current_sctx.sc_sid;