Appears to care about the high bit of a byte #5

We tried to use the emulator with a minicomputer emulator. The ASR33 always had the high bit set, a la sticky parity, but emulators have no UART in line so outputs the raw data that would go to the ASR33.

Anything from 0x00 to 0x7F is malformed, but obviously should be treated as valid ascii for compatibility, and anything from 0x80 to 0xFF should have 0x80 subtracted before rendering to emulate an ASR33 TTY. This would be like an "enhanced teletype compatibility" mode.