Handle final packet(s) from VDP after switching to terminal mode

[sijnstra]

After switching to Terminal mode, data flows back to the ez80 over the UART, which means that it needs to be handled by the incoming software to prevent bad input. For completeness, as Dean has pointed out, this packet could be read by MOS to update SYSVARs which means the screen dimensions would be appropriately updated.

An example packet received is:
86 08 80 02 E0 01 50 3C 10 00 11

Thanks,
Shawn