patch 8.1.0211: expanding a file name "~" results in $HOME

Problem:    Expanding a file name "~" results in $HOME. (Aidan Shafran)
Solution:   Change "~" to "./~" before expanding. (closes #3072)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 97242f6..a9f6c5b 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3801,7 +3801,7 @@
     else
     {
 	len = (int)STRLEN(fname);
-	(void)modify_fname(mods, &usedlen, &fname, &fbuf, &len);
+	(void)modify_fname(mods, FALSE, &usedlen, &fname, &fbuf, &len);
     }
 
     rettv->v_type = VAR_STRING;