For anyone following this thread and having as much trouble as I am, here is what I have accomplished so far:
The compiler error /wacom_serial/wacom_serial.c:144: error: implicit declaration of function 'input_abs_set_res' occurs at line 144 in the source. The same 'input_abs_set_res' is also used on lines 145, 175 and 176. To verify that this is not a secondary error, I commented out those four lines. The compiler completed successfully. There were warnings of course because now the code has holes in it. But, it does prove that the original error is valid.
When I get this thing worked out the fix will posted here. User Tokenrove has done a fine job of giving us Wacom protocol 4 users a chance of working with our tablets again. It will be a fitting 'Thank You' to him if we can report success.