patch 8.1.0569: execute() always resets display column to zero

Problem:    Execute() always resets display column to zero. (Sha Liu)
Solution:   Don't reset it to zero, restore the previous value. (closes #3669)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index d3bacad..51e0699 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3262,6 +3262,7 @@
     int		save_redir_execute = redir_execute;
     int		save_redir_off = redir_off;
     garray_T	save_ga;
+    int		save_msg_col = msg_col;
 
     rettv->vval.v_string = NULL;
     rettv->v_type = VAR_STRING;
@@ -3304,6 +3305,7 @@
     ga_init2(&redir_execute_ga, (int)sizeof(char), 500);
     redir_execute = TRUE;
     redir_off = FALSE;
+    msg_col = 0;  // prevent leading spaces
 
     if (cmd != NULL)
 	do_cmdline_cmd(cmd);
@@ -3336,9 +3338,9 @@
 	redir_execute_ga = save_ga;
     redir_off = save_redir_off;
 
-    /* "silent reg" or "silent echo x" leaves msg_col somewhere in the
-     * line.  Put it back in the first column. */
-    msg_col = 0;
+    // "silent reg" or "silent echo x" leaves msg_col somewhere in the line.
+    // Put it back where it was, since nothing should have been written.
+    msg_col = save_msg_col;
 }
 
 /*