Fix bug reported by Martin Guy

* "picoLisp's tmr_delay() function contains
  references to PicoC"; Fixed now.

* New function: tmr_read()
  This needs a little more work. For now,
  (tmr-read) doesn't respond to the symbol
  'sys-timer. Otherwise, OK.

* Add support code to use (tmr-delay) and
  (tmr-read) from picoLisp.