phptal.engine for Drupal 6 contains some unnecessary code

1) It appears to be mistagged so that the DRUPAL-6--3 version is actually pointing at a non-functional phptal.engine 1.9; 1.10 looks like it ought to be reasonably functional.

2) phptal_engine_preprocess is no longer necessary; most of that functionality was moved to template_engine_preprocess, so leaving it in will be duplicating the code. (Yay, stripping code out!)