CC Update: removes TERMCLEARALL command from the driver, attaches
terminal reset to the end of every transaction. The POS-side
command "termreset" does everything TERMCLEARALL would so there's
no longer a need for the back-and-forth. This specifically addresses
an issue where the transaction's end would sometimes be interrupted by
a message from the terminal. pos2.php is also more aggressively
ajax-y, which seems to help performance in general as well as this
specific issue.