Fix handling of repeat commands.

There were two approaches, neither were perfect.

One approach used the variables, last_command_hi=0 & last_command_low=0.
This ignores the fact that both field and channel can change. Plus
these variables weren't being cleared when characters were received.

The other approach used the per field/channel data members,
wb->data608->last_c1 and wb->data608->last_c2.
Thes variables weren't being cleared when a repeat command was received.

The fix: comment out code that uses the variables, last_command_hi=0 &
last_command_low=0 and clear the per field/channel members when a repeat
command is received.