Fix delete key setting a control character in wmEvent::utf8_buf

The check for control characters didn't account for delete (127).
This wasn't noticeable in most cases as delete is mapped to delete text.
Pressing Shift-Delete would enter 127 control character in the
text-editor, 3D text & Python console. This happened X11 & Wayland,
I didn't check other platforms.

source/blender/windowmanager/intern/wm_event_system.cc

@@ -5670,7 +5670,9 @@ void wm_event_add_ghostevent(wmWindowManager *wm, wmWindow *win, const int type,
         event.utf8_buf[0] = '\0';
       }
       else {
-        if (event.utf8_buf[0] < 32 && event.utf8_buf[0] > 0) {
+        /* Check for ASCII control characters.
+         * Inline `iscntrl` because the users locale must not change behavior. */
+        if ((event.utf8_buf[0] < 32 && event.utf8_buf[0] > 0) || (event.utf8_buf[0] == 127)) {
           event.utf8_buf[0] = '\0';
         }
       }