Fix dead link to USB keycodes doc (#3050)

* Fix dead link to USB keycodes doc

Link was dead and the fresher version I could find on usb.org is still older than this one.

Thus, WaybackMachine seems the best option.

* Fix dead link to USB keycodes doc, with 2 options

Give the WaybackMachine link (fresher and for reference of the content of the original link) and the usb.org one (older)

tmk_core/common/keycode.h

@@ -17,7 +17,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 /*
  * Keycodes based on HID Usage Keyboard/Keypad Page(0x07) plus special codes
- * http://www.usb.org/developers/devclass_docs/Hut1_12.pdf
+ * https://web.archive.org/web/20060218214400/http://www.usb.org/developers/devclass_docs/Hut1_12.pdf
+ * or http://www.usb.org/developers/hidpage/Hut1_12v2.pdf (older)
  */
 #ifndef KEYCODE_H
 #define KEYCODE_H