Tweeks to teletype emulation and testing on various browsers.

[jgharston]

// Updates by JGH, Apr-2021 // CHR$127 ignored, CHR$8 backspace, CHR$9 TABs expand option // single-spaced lines, >CHR$96 forced to upper case, CHR$96=UKP // CHR$95 prints underline using half-spaced hyphen, CHR$12 formfeeds // BS, TAB, ESC, Ctrl-Letter return keypresses // BUGS: Firefox: prevents Ctrl-N, Ctrl-T, Ctrl-W, impossible to prevent this // Chrome: almost all CHR$<32 intercepted by browser, including ESC and BS // SeaMonkey: returns all control characters

See mdfs.net/tty for installed example.