Always send M110 with the new line number (default 0)

Previously it worked since the first command of every print was forced to be an M110 and the line number at the beginning of each print was always forced back to 0 as well. Now it just uses the actual line number (increased on each sent of a checksumed/numbered line) and resets that when an M110 is encountered. What was missing was forcing the line number of the actual M110 command to the desired line number as well. Should be "more correct" than before now, and work.