patch 8.2.4336: using :filter for :scriptnames does not work

Problem:    Using :filter for :scriptnames does not work. (Ben Jackson)
Solution:   Call message_filtered(). (closes #9720)

src/scriptfile.c

@@ -1658,10 +1658,13 @@ ex_scriptnames(exarg_T *eap)
 		    i,
 		    si->sn_state == SN_STATE_NOT_LOADED ? " A" : "",
 		    NameBuff);
-	    msg_putchar('\n');
+	    if (!message_filtered(IObuff))
-	    msg_outtrans(IObuff);
+	    {
-	    out_flush();	    // output one line at a time
+		msg_putchar('\n');
-	    ui_breakcheck();
+		msg_outtrans(IObuff);
+		out_flush();	    // output one line at a time
+		ui_breakcheck();
+	    }
 	}
     }
 }

src/testdir/test_filter_cmd.vim

@@ -190,4 +190,10 @@ func Test_filter_display()
   bwipe!
 endfunc
 
+func Test_filter_scriptnames()
+  let lines = split(execute('filter /test_filter_cmd/ scriptnames'), "\n")
+  call assert_equal(1, len(lines))
+  call assert_match('filter_cmd', lines[0])
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4336,
 /**/
     4335,
 /**/